Strange timing and severe hesitation problem

[90blacktsiawd]

So i just got my car back from getting a new head, tranny, cams and turbo on. I then put a new front mount on as well. I was having a problem with idling but eventually the ecu learned the new setup and its better now though not completely gone. I did a search but couldn't find any one with the exact same symptoms. My car won't get over 4k if I'm giving it some gas. The turbo starts to really spool at 3k and starts to pull harder up to 4k which seems to be were the car should be taking off. It's like i just hit my stutter box. A puff of smoke comes out, the exhaust pops and it just can't get through the rpms. It's definitely not fuel cut. I've experienced that before and this isn't it. If i very lightly push on the gas i can get up to about 5.5k but then it stutters to hesitate. If i free rev it in neutral i can hit 6k before it does the same thing. I'm not knocking when this happens, i have all boost leaks up to 23psi fixed, plugs and wires all look good and are only about a month old and messing with my translator doesn't do anything wether i richen it up or lean it out. Plugs are gapped at .28. Also my o2's seem to be fine when i get on the gas. around .90 - .92.

Now for the weird timing issue. When i got the car back the mechanic had the timing set at 20 BTDC! I fixed that and have it down to 5-6 BTDC now. When i ground out the ecu and lock the base timing in it holds steady but jumps to 10 BTDC and you can hear it in the motor when this happens.

I'm going to pull the ECU today to make sure it doesn't smell like fish but it's already had the caps replaced about 3 months ago. Please help on this one I'm totally stumped.

 

[DSM90AWD]

Definitely sounds like you're running rich > 4K.
Have you tried to lower your boost to see if that helps?

Was you car running well with the MAFT / Stg3 chip and 650s prior to the Head/Cams/Turbo/FMIC?

Just to be safe, I'd double-check the T-Belt alignment as I've been burned more than once by a shop whom f-ed this procedure up. Quick way is to align the cam sprockets with both dowels at 12 o-clock and the exh pointer at 3 o-clock and int pointer at 9 o-clock directly opposing. At this point the timing pointer on the crankshaft pulley should be at TDC on the scale. If it's not, then put a screwdriver in the #1 sparkplug hole and turn the CS pulley until its at TDC and check the alignment of all the pointers.

Another thing to check is that the CAS is not 180deg off (easy 10 min job to check). If it is, would screw up the injector firings but car would still run.

 

[90blacktsiawd]

Definitely sounds like you're running rich > 4K.
Have you tried to lower your boost to see if that helps?

Well when this first started happening i was only running 7psi. I can't turn it down any further. Though that was with soem boost leaks. I also tried to turn the fuel down on the maft. 10% mid and 5% high. Still did that same thing at exactically 4k but my o2's were now at .98 instead of .90-.92 like normal.

Was you car running well with the MAFT / Stg3 chip and 650s prior to the Head/Cams/Turbo/FMIC?

Yes the was running good with all that before hand. Only time i would get a stuttering problem was when it was time to change plugs. But that was in higher rpm's and i could get through that and keep accelerating. Now i hit 4k with some load and it just won't get past.

Just to be safe, I'd double-check the T-Belt alignment as I've been burned more than once by a shop whom f-ed this procedure up. Quick way is to align the cam sprockets with both dowels at 12 o-clock and the exh pointer at 3 o-clock and int pointer at 9 o-clock directly opposing. At this point the timing pointer on the crankshaft pulley should be at TDC on the scale. If it's not, then put a screwdriver in the #1 sparkplug hole and turn the CS pulley until its at TDC and check the alignment of all the pointers.

I was thinking along those lines. Kind of scary if a specialist like DSMotorsports can't do a timing belt job. Of course the mechanic was adjusting my timing and idle without grounding otu the ecu or using a timing light. He would just bang the CAS with a wrench until it "sounded right". I called him on this and he said i was way off base. I went home and the SOB had my timing set at 20 BTDC.

Another thing to check is that the CAS is not 180deg off (easy 10 min job to check). If it is, would screw up the injector firings but car would still run.

Another thing i thought of but how do i tell if it's reversed? I've been looking around on the forums and haven't come up with an answer to that yet.

Any thoughts on the little blip i get in my timing when the ecu is grounded out? Thats an odd one I've never seen something like that before. It's definitely noticeable. You can hear the tone of the motor change for that quick second.

 

[DSM90AWD]

Another thing i thought of but how do i tell if it's reversed? I've been looking around on the forums and haven't come up with an answer to that yet.

There is a very small dot on the CAS gear and the CAS housing that should line up when at TDC. It's not very noticable and took me a bit to figure that out myself the first time I checked mine.

Any thoughts on the little blip i get in my timing when the ecu is grounded out? Thats an odd one I've never seen something like that before. It's definitely noticeable. You can hear the tone of the motor change for that quick second.

Are you also grounding out the terminal on the firewall or just the pin on the Diagnostic port? I alway s set mine using the firewall terminal and may jump a bit when blipping the throttle but not too much. With the engine at operating temp, fans unplugged and idle properly set, timing should be at 5 BTDC.

 

[steve]

Any thoughts on the little blip i get in my timing when the ecu is grounded out? Thats an odd one I've never seen something like that before. It's definitely noticeable. You can hear the tone of the motor change for that quick second.

What's your idle speed? when this happens?

Steve

 

[90blacktsiawd]

What's your idle speed? when this happens?

Steve

Well when this was happening over the weekend it was about 900 rpm's. Another problem i had when i got the car back was idle surging and it not wanting to stay started. I got it fixed. Seemed like the ecu just had to learn all the new parts. Well i came back yesterday. Started surging again after work and dying on me if i let the rpm's drop too fast. Like push the clutch in at 2000 rpm's and up. If i bring it down to about 1000 rpm's in 2nd before i put the clutch in it won't stall on me.

 

[DSM90AWD]

Well when this was happening over the weekend it was about 900 rpm's. Another problem i had when i got the car back was idle surging and it not wanting to stay started. I got it fixed. Seemed like the ecu just had to learn all the new parts. Well i came back yesterday. Started surging again after work and dying on me if i let the rpm's drop too fast. Like push the clutch in at 2000 rpm's and up. If i bring it down to about 1000 rpm's in 2nd before i put the clutch in it won't stall on me.

Did you set your base idle prior to setting the ignition timing? Your ECU will use the ISC to get your idle to keep in the 750RPM range (unless your Stg3 EPROM is set otherwise), so if out of it's adjustment range, you would need to adjust the BISS to allow more/less air to bypass the TB.

BTW.. the grounding out of the diagnostic port pin zeroes out the ISC for the above base Idle setting.

 

[90blacktsiawd]

Did you set your base idle prior to setting the ignition timing? Your ECU will use the ISC to get your idle to keep in the 750RPM range (unless your Stg3 EPROM is set otherwise), so if out of it's adjustment range, you would need to adjust the BISS to allow more/less air to bypass the TB.

Yes i did do te idle first. And yes my chip is set for a 900 rpm idle.

BTW.. the grounding out of the diagnostic port pin zeroes out the ISC for the above base Idle setting.

So let me get this straight your sayin i should ground out the diagnostic port to set the base idle? What about timing? And to do this i could just leave my logger plugged in correct?

 

[steve]

To set the base idle speed you ground both the timing connector in the engine bay and the diagnostic pin (pin10) on the DLC. Like DSM90AWD said this moves the ISC to it's default position (not zero), if it's working, so that you can adjust the BISS.

Note that this is why you can't have a datalogger connected when you set the timing because it will ground the DLC pin and you will really have the ECU in base idle speed mode rather than timing adjustment mode

Since the timing effects the idle speed you also need to set it and then go back and adjust the BISS.

The code in the ECU for adjusting the timing using the CAS will drop out of the fixed 5 degree advance if the idle speed goes above 1200 rpm.

All of this also depends on the Idle Position Switch, on the back of the TB, working.

So, you should clean the throttle body, pull the ISC to test the coils (on a '90 you can just disconnect the harness to reach the pins on later cars it's hard to reach the pins with the ISC installed), check the IPS, pressure test the intake looking for leaks, then set the base timing and base idle speed.

Steve

 

[90blacktsiawd]

Ok so let me get this straight. Leave the logger plugged in to set the idle and unplug it for the timing correct?

 

[steve]

Yes, but you have to get the timing right before you can do the final idle speed setting and you have to keep the RPMs under 1200 to set the timing.

Steve

 

[90blacktsiawd]

Ok so i checked the timing belt yesterday and the dowel's and timing marks all lined up with TDC. I couldn't get the CAS off the car to check. I'm pretty sure i found the problem though. I pulled all the wires off the coil packs and had someone try to start the car. Only one of them was really arcing. So my guess here is when i'm not in boost it has enough spark to ignite the gas but once boost comes on it just blows the weak little spark out. I borrowed and coil and power transistor from a buddy last night so i'll swap those in today and see if it fixes things.

 

[blue92laser]

VERY IMPORTANT...

I see the timing belt was done, in all this mess. Did you check the timing belt to make sure the cam gears are lined up TDC with the crank. Its important you spin the cam gears around to see if there at 12 o clock. Whats even more important is to see if the crank is at TDC. Take the number one spark plug out, the one closest to the timing, and insert a long skinny screw driver, rotate it to the TDC and rotate the crank back and forth little by little until you think the screwdriver is at the highest point its going to reach, then take a look at the cams.

Depending on how off the teeth are and which way the cams are rotated will choke your engine from revving high. I ran into the problem once. Also, the cam sensor should be rotated, just to see if that helps.

 

[90blacktsiawd]

Ok well back to the drawing board. I swapped out the coil packs and power transistor for ones that definately work and it didn't change anything. So now im back to being clueless.
i've made a few logs but i don't know how to upload them to my pc. And even if i could how would you be able to tell what value was represented at each point? So anymore ideas guys?

Blue92 did you have a problem similiar to mine when your timimng belt was off?

 

[90blacktsiawd]

Oh ya one more thing. The amount of boost does't seem to fix the problem. Wethwe it's 7psi or 18psi it still does it at the same spot. Another odd thing is that when i make changes on my transalator the o2 voltage doesnt change. I literrally drop like 20% fuel off WOT and the o2's changed from .92 to .90. That doesnt sound quite right to me though

 

[DSM90AWD]

With my 1990 properly tuned I see O2s in the .86-.90V under WOT. Anything much over .90V is too rich (on my car) and causes breakup at high RPMs, or is an indicator that I'm knocking and timing is being pulled.

I assume your Stg3 chip is calibrated for your 650injectors and the MAFT (1G MAS)? If it were me (knowing the MAFT can be a tricky bugger to tune) I'd take the MAFT out of the equation and re-install your 1G MAS just to see if that helps

 

[90blacktsiawd]

With my 1990 properly tuned I see O2s in the .86-.90V under WOT. Anything much over .90V is too rich (on my car) and causes breakup at high RPMs, or is an indicator that I'm knocking and timing is being pulled.

Well im definately not knocking i can see that on my logger. TIming doesn't look to bad though. Between 14-17 degrees advance. This is was at 17 psi last night in abotu 70-75 degree weather. I'm going to through some new plugs in today and re-inspect the wires a third time.

I assume your Stg3 chip is calibrated for your 650injectors and the MAFT (1G MAS)? If it were me (knowing the MAFT can be a tricky bugger to tune) I'd take the MAFT out of the equation and re-install your 1G MAS just to see if that helps

Yes it is calbrated for the 650's. And taking out the MAFT isn't an option. For one i sold the stock one. 2 i would have to take my frount mount off. I'm going to make my first attempt at fine tuning the MAFT today. One of the RPM breakdown points is 4k rpms.

When the stuttering happens the car does go rich. Real rich like .55 o2 voltage rich. But i figured this was more along the lines of the car is misfiring so of course it'll be rich with unburnt gas in there.

 

[DSM90AWD]

2 i would have to take my frount mount off.

To test you can always leave the GM MAF in place just disconnect the MAFT and re-connect the 1G MAS. If you ever want to try I can lend you my old one.

When the stuttering happens the car does go rich. Real rich like .55 o2 voltage rich. But i figured this was more along the lines of the car is misfiring so of course it'll be rich with unburnt gas in there.

The higher the O2 voltage the richer you are, the lower the voltage the leaner. .55V is likely a misfire (bad injectors?) or fuel cut. I did tell you to check the CAS which you say you still havent

 

[90blacktsiawd]

To test you can always leave the GM MAF in place just disconnect the MAFT and re-connect the 1G MAS. If you ever want to try I can lend you my old one.

I'll keep that in mind if i don't get this figured out thanx.

The higher the O2 voltage the richer you are, the lower the voltage the leaner. .55V is likely a misfire (bad injectors?) or fuel cut. I did tell you to check the CAS which you say you still havent

I don't remember where but i had always been told low was rich and high was lean. The injectors are rather new. Maybe 2k on them. It's definately not fuel cut. I've experienced that and this isn't it. Not to mention it will happen at 7psi all the way to 17 psi so it has to be somethign else. And i tried to check the CAS but i couldn't get the damn thing off. Is there some trick i'm missing? I unbolted it and tried to wiggle it free but that sucker wouldn't budge. I will give it another go today though.

 

[DSM90AWD]

And i tried to check the CAS but i couldn't get the damn thing off. Is there some trick i'm missing? I unbolted it and tried to wiggle it free but that sucker wouldn't budge. I will give it another go today though.

It comes off pretty easily (don't even need to unplug). On mine there was a black bracket that connected to the left CAS mounting stud and the throttle body, so make sure that is not in the way. Once both nuts are removed it pops right out.

Just make sure to disconnect your (-) battery cable and set your engine to TDC when re/re the CAS or the "alignment dot" trick won't work

 

[90blacktsiawd]

Ok well i have another update. I checked to make sure the CAS was lined up right and it was. I even switched it just to try and the car ran exactically the same. I borrowed another one from a buddy and threw that one on and once agian no difference. I threw in new plugs and reinspected the wires agian but none of that helped.

It seems to me that the motor is missing even at idle. Cylinders 1&3. As i was doing the timing again i noticed that the flashes on the timing gun were alittle random but went with the tone of the motor. So i checked all of them and 2&4 were just constant steady flashes and 1&3 were steady with some random flashes that you could hear as the car was idling.

Well next step is to borrow a buddies 90 ecu and some 450cc injectors to see if that will help. After that the only other things i can think of is the MAS and maybe the wiring going to the coil pack from the ecu. But the fact that it's 1&3 missing makes me think it isn't the coil packs at all.

 

[DSM90AWD]

The ECU could definitely be the problem since you've eliminated most other possibilities related to ignition.

Just a couple other thoughts.
- Have you performed a compression check since the problem started? I recently installed a set of FP2s and one of the followers was not centered on the perch causing erratic idle and extremely low compression in that cyl (how I diagnosed it).
- Also you said you checked for boost leaks, but is it possible you still have one between the turbo and intake?

Re-reading your first post, you say the only part added after you got the car back from DSM was the FMIC? I assume that the car ran fine at this point but only after the addition of the FMIC? Is it possible that something (a coupler packaging..etc) was injested and is restricting flow? Sounds stupid, yes, but the same thing happened to me when my 16G rubber "adaptor" got stuck sideways in my intake

 

[90blacktsiawd]

The ECU could definitely be the problem since you've eliminated most other possibilities related to ignition.

Just a couple other thoughts.
- Have you performed a compression check since the problem started? I recently installed a set of FP2s and one of the followers was not centered on the perch causing erratic idle and extremely low compression in that cyl (how I diagnosed it).

I have not perofrmed a compression test since but your right i definately should.

- Also you said you checked for boost leaks, but is it possible you still have one between the turbo and intake?

Funnt you should say that. I took my car over to JNZ tuning to get the boost leak test done because i'm imooatient and wouldn't be able to do it myself for atleast a week. We got all leaks up to 23psi. The last one was the inlet to the turbo. Now the way my turbo is set up is that the intake doesn't bolt directly to it like a 16g. It has an adaptor that bolts to the turbo then the intake gets connected to that. It's pressed up agianst the lower radiator hose so one side is alittle flat but it doesn't seem to have a bad connection. Think this might ba a problem?

Re-reading your first post, you say the only part added after you got the car back from DSM was the FMIC? I assume that the car ran fine at this point but only after the addition of the FMIC? Is it possible that something (a coupler packaging..etc) was injested and is restricting flow? Sounds stupid, yes, but the same thing happened to me when my 16G rubber "adaptor" got stuck sideways in my intake

Well i honestly can't say wether or not it was doing this before the front mount. Jon at TRE was very specific about babying the new tranny for 500 miles. I only had about 100 when the FMIC went on. So i never got up to 4k where the problem is occuring. I'm relatively certian that nothin is stuck in the piping anywhere but i do have to pull the FMIC off when my new UICP gets here so that will be a good time to check.

Another thougth i had. My UICP is a little longer than it should be. There is no transition from 2.5 to 3 at the mas. So the piping is directly agianst the mas itself. I was wondering if maybe this is a problem. I could see how once alot of air started woving through here some turbulance might occur. I told JR at extreme intecoolers and he's sending me shorter pipes which should be here today so i can try them this weekend. I'm also going to try a buddies GM mas to see if that makes a difference.

 

[90blacktsiawd]

Ok i pulled the ecu and threw a stock one in. I left my 650's in a compensated with them on the maf-t. Same thing happened but at 5k this time. So this really had me thinking tuning. Which 90dsmawd said in the beginning and i had already turned my fuel down by 20%. I said F it and turned the fuel down by 35% and what do ya know i can pull to 7k now. I feel like an dumbass right about now but atleast it got worked out. Now i did coem to find that someone had messed with the setting on my maf-t. They had the 1st knob which is used to pick 1g or 2g and start to set for injectors turned to F. Now F isn't even a dsm. 0-3 is a 1g and 4-8 is a 2g and the rest aren't used for a dsm. Now i know I didn't do that and there is only one place (the shop that did the work) that had access to do that. Makes me wonder if they were trying to get alittle more money to "fix" this problem that i'm thinking they started.

But anyways i'm totally confused as to how i am currently running 50% leaner on WOT with a T04B at 17 psi than i was running 18 psi on an evo3 16g. If someone could explain that please do. Anyways Thanx very much 90dsmawd for all your help. You should be next in line for wiseman status.

 

[DSM90AWD]

But anyways i'm totally confused as to how i am currently running 50% leaner on WOT with a T04B at 17 psi than i was running 18 psi on an evo3 16g

I recently added a 50-trim and FP2s and my tuning didn't change much, so your need to radically subtract fuel is evidence something is not right.

But you're now running a stock ECU right (i.e. no Stg3 chip)? If so, since 650s are ~45% larger than 450s so would expect -50% corrections to work

I'm no MAFT expert by any means, so cannot comment on the settings you specify. You may want to post up on the http://www.fullthrottletech.com site if you have any specific questions.

I do know that it is very important to make sure that the MAFT and EPROM are not in conflict w.r.t. calibrations. If you calibrate for the 650s with the EPROM, then you should set the MAFT to the factory settings (i.e. 450s).

Keep us posted on your progress