bogging with boost increase

[GST with PSI]

i have searched the archives in and out and couldn't find a problem that sounds like the one i'm having.

-90 manual trans eclipse gst almost stock
hallman manual boost controller
k&n filter
3 inch cat and exhaust back

when accelerating the car has a loss of power that feels like bogging, no bucking. it's not violent. it comes at WOT or close to WOT. at stock boost level the car has the problem but on and off as rpm increases. it seems intermittent under low boost conditions. as boost is turned up the problem gets worse, at about 13-14 psi the car does it constantly as long as the throttle is mashed the car will constantly hesitate. during hesitation the car still runs well and pulls steadily but with complete loss of power. the car actually pulls harder under stock boost pressure than at 13 psi. this car idles perfect but sometimes a quick miss is herd. the miss is instant. car runs perfect at partial throttle. when boost is turned up to 13 psi hesitation can be controlled with throttle, meaning when the car starts to hesitate, i let off the throttle lower the boost and stop the hesitation.

the following is a list of things i have already ruled out:
-this is NOT a boost leak. i tested my system form the compressor outlet on at 20 psi
-compression test is 119 psi across the board
-new plugs denso iridum
-not a vacuum leak throughly checked
-new fuel filter
-not fuel cut
-timing at idle 8 btdc with computer enabled (my logger tells me so)

i haven't had a chance to log a 3 gear pull but if that data will help in the diagnosis please let me know. what would be really helpful is a log recorded by a nearly stock 1g gst for me to compare to. my brother runs 17 psi on the same stock 4g63 and fuel system i have so i know the actual boost level is not the problem. i would be more than grateful for any help anyone could give me. also anyone who makes it obvious they know everything about dsm's and has an ignorant ass comment to add can save it.


thanks guys in advance

 

[vr6chris]

Problem sounds like a misfire of some sort. problems might be a number of things. such as coil, wires, o2 sensors

 

[GST with PSI]

i'm going to try my friend's coil on plug setup and see what that does......

 

[ddavisaf]

Why? You OBVIOUSLY have spark, or else your car wouldn't get to WOT let alone idle.

Your problem lies in your plugs.

NGK BPR6ES

Gapped at .028-.3

 

[oldman]

-compression test is 119 psi across the board

How can you rule out those compression numbers, the service limit for 1G is 121, I also find it hard to believe they were all 119 in every cylinder. I suggest double checking your testing procedure against this article and try a different tester to verify the result. If those numbers stand, a leakdown would be the logical next step.

 

[GST with PSI]

121 is only a reference point giving a technician an idea of where the compression should be. for the most part variation between cylinders would indicate a problem, not simply number a bit low in all cylinders. a compression test could actually vary at least 10 psi depending on your altitude according to sea level. my shop manual allows for no more than 10% variation between cylinder, thus leading me to believe my compression is
a-ok.

 

[GST with PSI]

Why? You OBVIOUSLY have spark, or else your car wouldn't get to WOT let alone idle.

Your problem lies in your plugs.

THANK YOU so much! i just realized how dumb it was to buy the wrong name brand name.
i was so stupid to think a brand new set of denso iridium plugs would work as well as a set of NGK's. i'm sure that will fix my problem.

 

[oldman]

121 is only a reference point giving a technician an idea of where the compression should be. for the most part variation between cylinders would indicate a problem, not simply number a bit low in all cylinders. a compression test could actually vary at least 10 psi depending on your altitude according to sea level. my shop manual allows for no more than 10% variation between cylinder, thus leading me to believe my compression is
a-ok.

Not true, 164 is the reference point and 121 is the service limit. I do think it can be a tester problem because they were all exactly 119 across, reason why I suggested re-testing with a second tester.

 

[BergayaJS]

Why? You OBVIOUSLY have spark, or else your car wouldn't get to WOT let alone idle.

Your problem lies in your plugs.

NGK BPR6ES

Gapped at .028-.3

i like this reply. but yeah it's your plugs + gapping. Common problem for me when I first got my dsm + being so blur till i got my NGKs

 

[ddavisaf]

Just trying to be helpful

As to the compression test, I totally agree with Bruce here. You definately want to re-do the test. However, with dry and wet testing. If you're still getting the same results look into a leak down test.

It can't hurt, only help right?

 

[GST with PSI]

what problems did you have before switching to ngk plugs?

 

[BergayaJS]

what problems did you have before switching to ngk plugs?

Well bogging under boost? And your problem wouldn't be fixed right when you get your ngks, you gotta make sure the gapping is correct.

 

[94Jettameowpsst]

Your compression may have a great deal to do with it cause if its that low, chances are you're getting a lot of blow by and you could be fouling out your plugs. Does your car smoke at all? If so, it could be ^ that, could be your head gasket as well. If your car doesnt smoke, then maybe your fuel pump is on its way out cause mine did the exact same thing. Sounds like a subbie up top and even more so when the rpms increase. Just a few things to look at.

 

[92 GSR-4]

If your compression test was performed correctly, then you should check out that problem, probably the rings if it is a consistent 119 across the board (give or take a few). But that isn't your problem with rough running. I have seen a DSM run just as smooth as mine on 3 cyinders and hit low 13's before realizing there was 0 compression in one cyl.

I don't believe the NGK's can clear everything up, although I DO use BPR7ES's , but Im running a 12 sec semi modded car. I think you may find your problem with a logger. Check out that airflow signal for one thing, also keep an eye on your O2's, you may see an irratic signal coming from the airflow sensor. It would be something like a normal upwards curve and then just jump way up and come down. This would make the ECU add a whole bunch of fuel (bog) and maybe hit a very quick fuel cut (stutter).

I have seen this on a few DSM's, some of which had a bad airflow sensor, and others had some water actually get into their intake. GM MAF's are terrible about doing that, especially with a Cold air intake and a blow thru setup.

- Are you using a stock intake setup/ stock MAS?

- Have you checked your plugs to make sure there are no damaged wires or plugs?

Also, your ignition may have a problem. And maybe not just your coil/plug setup. Alot of times the ECU can cause a weak spark, this is an unfortunate side effect of our old-ass cars. This will cause some tuning hell. Email Dave Mertz @ DSMlink and he can service your ECU if you think that may be the problem. I have sent 10 or 12 to him so far with excellent results.

And last but not least...this maybe stupid, but when I first was tuning my DSM, I had those power transistor plugs by the T-belt cover shake loose one time....I thought I was losing a cylinder... Just make sure everything is plugged in secure. Good luck and let us know what you find!,


Seth

 

[GST with PSI]

new results:
my compression gauge has taken a crap. went and bought a new gauge and followed the test procedures specified in the link.....
149 153 149 149
the schrader valve on my old gauge was weak and leaking compression, also the first time i only turned the motor over 2 revs . my manual never specified a specific number. however thes test turned out well and i am still happy with my compression results.

due to popular demand i am also going to get a set of ngk's. if the perform the same as my current set i am also going to burn someone's porch down.

i still am using my stock mass and intake setup. i have switched it out with a confirmed working unit with no results.

i suspected possibly my wires or coil my be at fault. i was planning on trying my friend's coil on plug setup to eliminate both the coil and wires as problems, but my car is a 90 year model. as you all know the ignition coil plug on a 90 car has a 4 prong connector instead of a 3. i was thinking about trying to make an adapter plug to convert my 4 prong to a 3, but wasn't sure if it could be done. if i could do it i;m pretty sure my tach wouldn't work, but i don't really know. anyone done this or have any ideas?

 

[madmader]

, arnt NGK denso nipidenso blah blah blah the same plug company just made in diffrent country's......


you just have the wrong type plug for boost. same plug manufacture.... if you all didn't know.

 

[madmader]

I have a march 89 pruduction GS T and I have the same problem you are talking about. It is intermident. Right now for the past week it has been fine, but last week at the strip I was bogging. I have an old HKS EVC and it bogs down when I have it on some times. It might be the EVC or could be somthing else.

I have 3 setings. 10 psi, 13 and 15psi. Then stock with it off is around 8psi. I ran it bogging in all 3 stages of the EVC, then tuned it off and it was fine. Also a couple days later it boged with it even off. And then my car backfired and almost died. Turned out the battery was dead and my 80 amp alternater fuse blew. It ran fine after that, but intermidintly still does it.

I have no idea why, but i will some day find out why.


I run NGK BPR7ES

 

[Spoolin4Ever]

OK, there have been some good suggestions, now I will throw some in:

1. TPS (sometimes it takes a while to throw a code when it's going out). Simply unplug it and drive your car, if it runs better, that was the culpruit (yes the cars run without 'em)

2. ECU

3. Clogged air filter or intake.

4. Leaking throttle body shaft seals (just throwing it out there)



If i am incorrect, please don't burn down my porch.