well I'm new to thirdgen.org not to my car though, ive had my car for 5 years. Here is my problem. Let's say I'm at a red light, when I'm at idle my car shakes alot its not smooth at all, and once I take off on green it chokes not in a big way just a small choke, but if i punch it at a green light it acts normal, this is so weird because all my injectors are not that old they are about 6 months old, ive changed sensors (all of them) plugs, distributor, wires, fuel pump, fuel pressure regulator. Now I don't know what to do because Im out of ideas. This problem only happens when my car is warm. And also I felt a small power loss. I feel the engine running right after 2000 rpm's. Help idk what to do. Could the ECM cause this???

 

what year car,and what engine?I'm assuming tpi, if so,are you running the egr?That could possibly cause the problem you're having.

 

my car is 1990 gta trans am. Acctually no the EGR is not connected, but even before the egr was disconnected it was running like this...its also weird because lets say i warm it up and i drive around thw block and come back to park ill cut it off and start it right back up the engine will run like new won't shake at all and it'll be so smooth but after like 20 sec it'll start with that gay problem again. Also throttle response is not right, SES shows tps sensor but ive changed it 4 times and the same thing happens

 

I don't know for sure,but does the 1990 tps use the non adjusting one like the 91-92 speed density setups?
If so,you may have a faulty ecm.

 

'90 is SD, has a non-adjustable TPS, basically whereever it's at is good for the ECM...it uses the idle setting to scale the rest of the throttle positions.

Even though the EGR is disconnected (hint, hint if you bought it that way), it doesn't mean it not getting some EGR at idle...you have to pull the egr (PIA) and make sure the pintle thing and seat are clean and not leaking...there's a lot of other things that can cause your problem, but I'd suggest fixing what you know is broke first, then go from there.

PS. EGR is not a bad thing, disconnecting/bypassing it actually hurts you and certainly gains you nothing.

 

actually the one I have has the 2 plugs that only allow it to be set at a certain position, but I took them off to adjust it thinking it would help, but didnt. I was told by another friend of mine that I should change the ECM. I just want another opinion...I was thinking of changing it because its the stock one from 90 and my car has well over 280k miles on it, acctually my ECM did go bad on me once, all my left four injectors went out and it was the ECM that caused it, but I just had it fixed.

 

Interesting on the injectors/ECM issue, I haven't looked at a SD ECM schematic for quite some time, but can assure you the MAF ECM's only have one quad driver to drive all the injectors(the QD is in the ECM)...only thing that would cause one bank not to work would be a bad fuse (INJ1 or INJ2-sans wiring issue)....just food for thought if you had to pay to get it fixed at a shop.

 

I am running speed density on my 89,and I purchased a custom prom from
www.tpiparts.net
It was programmed to delete vats and egr.So I guess the ecm knows if the egr is hooked up or not.

 

see the thing is when i was changing my distributer, the vac line that goes to the egr being so old broke and I haven't had time to fix it, but before this happened it was running like it is right now, like crap.

 

yes it was fixed by an auto electrician. Do u guys think that changing the ECM would help?

 

no comment on this?
And yes nightcrawler I would try another ecm.Helps if ya got a spare or a buddy with the same ecm.

 

my friend has an 88 gta but I doubt its the same connections..and also i have another way of explaning, just imagine v-tec on the hondas after 5000 rpm or so, the v-tec kicks in. Thats how mine feels but at low rpm. I punch it (WOT) and once it hit the 2000 rpm it hits the actual power of my engine. So I feel like I'm driving a v8 Honda. LOL

 

Yes,

The ECM now won't reconize or control ERG elctricaly, but mechanically, the EGR can still cause problems if not seated to seal off the exhaust gasses from entering the intake.

When you disable EGR in the PROM, you just eliminate control and monitoring, has no effect on mechanical perfomace of the device
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I don't think the ECM is the issue, the ECM is probably the most changed, but least effective fix on all EFI thirdgens.

I'd suggest fixing what you know is broke first (vacuum line comes to mind) and going from there.

So, just another thought pops to mind, why did you replace the dizzy, and how was it running before?

 

HAHA! No your friends ecm won't work BTW.

 

well thanks for that little lesson.
Maybe I should go in and remove the egr itself before I start having problems.

 

You seem to be taking offense to my post, I don't know why, and I wans't trying to belittle anyone, just posting factual information.

There's no need to remove your EGR if it sealed, plus all the work to pull the plenum is a PIA.

You can take my advice, or not, makes no difference to me, I just popped in to help, not start a pissing match.

 

hows the ignition timing and such? What is the base timing? are your spark plugs good and do you have a good ignition module in the distributor?

but does sound partially like a vacuum problem. fix that line or plug it

 

I'm gonna go ahead and fix all the vac lines and I'll update. I only wish you guys could drive my car so u guys can give me a more precise opinion. I really appreciate the advise...

 

I have an msd ignition system, spark plugs are 4 months old and the wires are also msd and those are about 3 months old. Timing is good haven't checked it but its not causing a problem

 

I'm guessing this was directed towards me?
If so,I have no offense issues.Just thought you meant by mechanical problems that possibly something could break or go bad in the egr itself,and I didn't mean to sound sarcastic at all,I really meant thank you for the lesson.
oh yeah,removing the plenum would be a pain,so I guess I'll leave my egr alone.

 

Yes, the post was directed at you...that's the problem with posting things, what one reads vs what one types, can easily be taken out of context. Tottally different word than sitting around bench racing.

Sorry if I sounded like an ***, we're good

 

not at all,thanks again




btw,back to subject.check your vacuum lines first man.

 

will do, if that doesnt work then i guess ima have to change the ecm...

 

FWIW for a side note here on the tps. the older adjustable tps 1986 will fit in place of the non adjustable one. If you can't get the .54 volts or 4.5 v wot this could allow you to hit the numbers.

 

so your telling me that the 86 tpi sensor would improve my performance??

 

This is the post I was refering to and only if a check of the volts is out of spec.

Sorry not to have tied it together.

 

"Timing is good haven't checked it but its not causing a problem"

How do you know its good and not causing a problem when you have not checked it?

There are a few items that need to be checked when there is a difficult to find issue with TPI cars. The basics are:

1) Fuel pressure is #1, do you have 43 psi fuel pressure, and when you turn off the engine, it stays up for at least 1 to 2 hours. Some people here will say that it should stay up high for a lot more than 1 or 2 hours.
2) TPS voltage at idle, and when you manually opened the throotle with the engine off (of course) does the TPS voltage rise evenly with no dead spots or spikes. (I think that you measure the TPS voltage with the key on and red probe to terminal A, and black to terminal B (I think, its been awhile for me).
3) Timing, check the timing with the ESC wire disconnected. I think that base timing should be 6*, but my 350 always ran better with 8* timing. And dont forget to reconnect the ESC wire!!!
4) Pull the valve covers and check the valve train. (I had a broken valve spring on my '99 SS which gave me a miss on number 6, making me think that I had an electrical issue)
5) Make sure the grounds to the back side of the cylinder heads are solidly attached, and no corrosion.
6) What is the IAC count at idle? The least amount of help from the IAC to maintain good idle is best.
7) Are the spark wires solidly attached at both ends. You might think that they are on correctly, but once in a great while I find one laying on there.
8) Is anything shorting out. I found an arc short out by running my engine at idle in the garage in the dark. An arc really shows up in the dark which you can not see in the daytime. You can laugh at this one if you want.

Years ago I had a power loss in my '87 350 IROCZ, it turned out to be a clogged fuel filter.

 

Thanx alot this is alot of good info. Its not my valves for sure its always acted weird since I got it I had the engine re-built and it acted the same. The problem acctually became worse at the track one night when it started acting like it had v-tec LOL... My times on the track went down by .200's of a sec