My car just started doing a very strange thing yesterday. Every three minutes (give or take a little) while driving my car will suddenly choke for about half a second, like it wants to shut off, but immediately turn back to normal. When this happens at idle it will cutout/choke for only the half a second and I notice my vacuum falls from the normal 18 to about 14-15, without doing anything to the throttle it stays at 14-15 vacuum for about 20 seconds then corrects itself back to 18.

I remember this exact problem happening to me a while back, but it went away after about a week.. Could it have something to do with my fuel system and the ECU doing some correction function? As I said it happens consitently about every 3 minutes. I am currently using one of the included S-FMU discs that gave me the lowest possible static fuel pressure - in case that helps at all. I know there are other rings for sale from Vortech, would one of those be better suited towards the 9-10psi 420a setup? Thanks for anyone's help! Damn DSM's and their annoying little quirks

When is the last time you changed your plugs and wires? i know i get slight hesitations every couple of minutes or so when my plugs start to foul out and wires start to go bad so this is just a suggestion.

Thanks for the help birdman. I pulled out my old NGK plugs and they were charred black, so I swapped in a new set of them. The car ran perfectly after that, but within an hour started to do the same damn thing again. As for the wires, they were put in by my mechanic a month ago. The thing about this problem that confuses me the most, is it happens EXACTLY every 2 minutes without fail. It is just a quick 'choking' effect on the motor that goes away once I feed the motor some boost. It will happen every 2 minutes no matter what the car is doing - at idle sometimes it will be enough to shut my car off where I need to restart. I don't want to know what it would do while I was under boost, so I don't feed the motor any boost when I know it's about to happen.

Sound like something ECU related? Perhaps the ECU is detecting something and trying to correct it or fix? Anybody know if the ECU does something like this every 2 minutes on the dot? Thanks!

my car used to do that.... sounds like its exactly the same problem.... at the time, i didnt know it, but my ecu was dying. i had to replace it and my whole idle control circuit (which had fouled out).

ecus are cheap. i got mine for 100 shipped to my door, and it is perfect. i got it from cherryauto.com (might be cherryautoparts.com) and they were great.

good luck, hope this helps....

That might be the problem then 97eclipsedgs. Thanks a lot for your insights.

I'm taking it down to my mechanic on monday and he will hook up the 'check engine' diagnosis machine and we will run it at idle and see what the ECU does every two minutes when this happens. It must be something electronic - that's the only way to explain a problem like this that happens at an exacting period of time. The car runs perfectly other than this annoyance. Fingers crossed.

Yeah, get back to us. I'm watching for an answer, I don't even have a suspicion of what TF.

did you gap you new spark plugs to like .32-.34 because if not that could also cause the chocking and misfiring. when you buy new ones for our cars they are usually gapped to .45 or so maybe .50 im not really sure. also i use a range colder ngk are you useing the regular heat range? check these things first before you go through the trouble of replacing the ecu then if that doesnt work mayeb check the ecu or re-tune you s-fmu

Originally posted by birdman
did you gap you new spark plugs to like .32-.34 because if not that could also cause the chocking and misfiring. when you buy new ones for our cars they are usually gapped to .45 or so maybe .50 im not really sure. also i use a range colder ngk are you useing the regular heat range? check these things first before you go through the trouble of replacing the ecu then if that doesnt work mayeb check the ecu or re-tune you s-fmu

Click to expand...

Well, it's definately not the S-FMU because this also happened to me back before I even upgraded to the S-FMU. I don't think the spark plugs are to blame as the gap is the regular stock gap and I've been using these same type of NGK's since day 1 with my car. I'll try the other heat range, thanks birdman

It actually stopped occuring this morning while I was on the freeway, and all the way through town. Then when I was driving back home today it started to happen, every 2 minutes again.

I'll let you all know what I find out.

yeah.... hope my info helped you

in terms of check engine codes, for a while (during the period of idle control problems and misfires like the ones you are describing) i was only pulling an 02 sensor code. however, what keyed us to focus on the ecu was that the scantool would sometimes just flash a "connection temporarily lost" screen, which meant that either the ecu had fouled out, there were shorts in the circuit, or the scantool was busted (and we knew it wasnt the third choice). then, with all of these problems continuing (the idle control problems and the hesitation/stalling) we began to tackle it by relpacing my idle control motor and my throttle position sensor. this didnt work, so then we decided the next step was to replace the ecu. we did that, and still no luck, so we replaced the idle control circuitry and that did the trick.

however, since you dont have any idle control problems, i would venture to guess that you just need a new ecu, which is virtually a buy, plug, and play job. what you might want to look into is getting some more air up into your engine bay via the side ducts on the front bumper. you can use drier duct to vent that general area. it gets really hot, and ive heard that cause the ecu to fry. good luck. let us know how everything goes!

dude seriously if your plugs are gapped higher then like .37 then it is def going to cause misfiring and hesitation even if it ran right before just make sure that you check that becuase it will save you some money

Alright, I've tried the different plug gaps and no candoo so I'm pretty sure it's the ECU that is causing the problem. I will be ordering a new one tomorow. If that fails to fix the problem I will try to replace the idle control circuit.. Thanks for the great help guys (girls? eheh).

I will keep you all posted as things progress.

same thing has happened to me.. and actually i started having problems with the car starting all together.. i went to the shop and they said my ECU was fried.. i knew that was a load of crap so i handled it myself.. i ended up finding out that the problem was the relay on the back firewall on the driver side. There are two relay's tied together with separate connections. I got a new relay and that was the deal.. one is the fuel pump relay which wasnt bad and the other was a relay sender that told the engine to fire spark and what not.. i dont know the acutal name to it.. MFI or something i thought.. dont know for sure.. Check and see.. My car choked so bad that it sometimes died if i couldnt give it some gas right away...

Now that you mention it, it has been taking more than one turnover of the ignition to start my car lately. Also, when I was driving home today while the car was warmed up and at normal temperature, the gauge just dropped to cold and stayed there for a few seconds then switched back to medium (normal) !! Hmmm maybe that could be the source of the problem? Aren't there two different modes of operation with a ECU and fuel control? - both hot and cold modes or something?

Damn my DSM is quirky lately

Well, I fixed the two minute choking finally. I first tried resetting the ECU, still didn't fix it. Then I started to look at my engine bay last night and noticed a lot of fluid on the top of my battery around one of the two battery vents. I disconnected and removed the battery and could see a few puddles of battery acid below - meaning it was leaking for some time I guess. It was kind of an old battery so I just decided to get a new one anyways. After putting the new one in it, and the ECU was naturally now reset again, everything worked fine..

However after driving it around for awhile I noticed some smoke coming from the driver side of the hood. I pulled over and popped the hood and there was fresh oil (or what I think was oil) all over the upper right side of my motor's head - the smoke obviously coming from the oil burning off of the side of the engine where some of the oil had covered. What the hell, now somethings leaking, great I could'nt see much as it was dark outside but I cleaned a lot of the oil up and drove it slowly home. I'm going to check everything out in my garage tonight and see if I can find out where this is coming from. There was only oil covering the upper right portion of the engine bay, strange because I don't think there is any component running oil through it on that side. Arrgg, this better be the last mystery problem to happen to me.

*EDIT* my oil light came on for a second while driving home then turned off, it's never came on before..

Don't know if anyone's even following this anymore but here we go again.

Oil (and now light smoke) was coming from the crankcase breather line (filter had blown off) on right side of the valve cover. I'm changing the old PCV valve first to see if that does anything. If not, then I'll inspect the head gasked (common failure on 420a) and put a sturdier aftermarket one in for good mesure. If not then the problem lies in oiling or further down below

hey man, glad you got to the bottom of problem #1....

as for problem #2... you may just be getting oil blowby past your rings... you can put a fuel filter on the valvecover instead of a breather filter, and that will keep oil from sprayin all over the place (this happened to me as well). if your head gasket is leaking, then your coolant would be brownish goop... so check that, and you can pretty much rule out your head gasket. hope this helps man....good luck!

Awesome. Glad to hear somebody else car has experienced the same quirks my car has been starting to do. Makes it easier to locate the real problem!

I've dedicated tomorow as my day to completely focus on my car. Fixing any recent inconvienience, annoyance, or damn interior rattle. Add a fuel filter as my crankcase vent (thnx 98eclipsedGS, you own), change PCV valve, oil & filter change, drain & flush cooling system out, add fresh fluid. Then do a thorough clean on the inside. I'm also going to take a look at the head gasket seeing as I have all day to work on my car. A compression check wouldn't be a very bad idea either..

My car's in for a treat tomorow

*edit* if the head gasket has failed what's a good internet site to buy a quality one off of? I have already changed the head gasket once and was hoping to not have to replace it again.

It has nothing to do with your HG. If the line came off your breather filter then it is blowby. The MLS HG from the dealer is the right one to use for the HG repair. The comp check is never a bad idea. Rather than use a fuel filter for a breather I would use a catchcan, that way you know how much is comming through.

Nice to hear from you again Kirby. I suspected the head gasket or a crack in the head itself could be part of the problem. There was a lot of white exhaust smoke coming from my car (exhaust and engine bay) from coolant now getting inside the combustion chamber and a huge loss in power. The oil blowby was more of a mystery to me as that could mean something giving way with my oiling system, or worse, something giving way in my bottom end. A quick compression test revealed the worst (but good in the end) - the oil was blowby on the first and second cylinder after compression showed around 80 for both cylinders.. so it's now time for an engine rebuild. I'm going to be out of a car for a couple of months while I save up and plan for the rebuild - thankfully my job is less than a mile away.

I played with fire long enough boosting this motor and now I have been burned. When the rebuild is complete and the motor is no longer a worry for me, I know it will all be worth it.

Pulling this ttt.

I have some of the similar problems. My coolant is brownish but not goop. And the oil coming out of the breather, which im working on now. I just bought a pcv valve and a catch can. Going to replace that and then see about a compression check.