90Iroc

My car lately has started to kind of hesitate. I thought that it might be due to a faulty fuel injector, from past experiences, but all the injectors check out at 17.1 to 17.8 being the highest resistance. They all fall within that range. I also thought that it might be arcing of the wires, but I can't see any signs of that either. My fuel pressure was down to 39.5 psi (I thought I had set it higher, but I didn't have a gauge when I set it the first time) when I checked it also, so I've turned it up to 47psi (I have a 305 TPI). I tried to check to see if my EGR valve was stuck but I couldn't get my fingers in there to see if it would move. The car isn't setting any codes, so I don't really know what to check next. Sometimes when I'm driving (by the way it's a 5 speed T5) I'll be cruising up to 3000 RPM and then it sounds like it's misfiring. Do you think that maybe my MSD 6A box is malfunctioning? I've heard that if you don't use the rubber grommets that it won't function properly after a while because of vibrations. Is that true? Mine and my brother's boxes didn't come with any rubber mounts. So therefore, I couldn't use any. What do you guys think? It doesn't do this all the time, when it does do it, I notice it mostly in overdrive at 50 MPH that's when the hesitation is the worst.
I'll be checking the timing tomorrow.

Grim Reaper

I suffered with the very same thing for years. Changed the EGR, it was gone at the time, cured the major problem but not the minor hesitation and stuttering that the car always had. Changed the pick up coi, helped but not totally, and on and on.

That was one of the reasons I got into eprom burning. I had noticed with my Diacom that when this happened, that my BLM/INTs went nuts momentarily. Had new sensors, so I was really left with only the eprom.

After playing with my eprom and making massive changes to my VE tables, Injector Flow constant, fuel pressure and playing with the TCC locking I finally got my car to run smoothly without any hesitation. Just to confirm, I reinstalled both my ADS and my stock GM eprom...and the hesitation returned.

A custom prom probably won't help as it involves really playing with it, but it might help.

If the car sounds likes it got a wicked cam (when it doesn't) and is really "jerky" at very slow speed (around 10 mph just prior to shifting in second), then it might be your EGR. That was the problem that made me changed the EGR and I was hoping the hesitation was related, but it the hesitation wasn't...just the other part.

90Iroc

The car is jerky in first at low speed. Maybe I will go ahead and change the EGR just to have a new one and have a new runner to intake gasket there. I don't know what that moisture could have been. Does anyone else know? Just water? Why would water be there? Condensation? By the way Glenn, I have an Ed Wright Eprom in the car.

Grim Reaper

I have never noticed any condensation on my intake, but I am not poking my nose in there possibly as often as you are now and it may be cool where you live right now. I asumme you have a water/glycol mixture so you don't have any coolant. If it is straight water in your cooling system, then it may be a coolant leak.

From you description, it sounds similar to mine when my EGR went. The hesitation I am talking about could happen anywhere, anytime. Most noticeable at part throttle. Felt like the engine just momentarily died and then came back.

There are so many "hesitations/stutterings" just like there is so many different types of engine "knocks". (I won't go there with that one).

Good luck, hope it does the trick. And monitor that "condensation/wetness". By any chance are you turning your a/c (or defroster) on? The condenser is often a source of "dripping water".

90Iroc

I've got the heater on, but even if it's not on, it'll do that jerking thing, where it feels like it lunges at low speed. You Know? The bolt that had backed out and where I noticed the moisture was at the middle bolt of the upper runner to plenum bolt. Why and how could water, moisture get there? It's on the passenger side. Hey Glenn, here's another question: I don't have emissions testing here in Indy, I know that the EGR has something to do with emissions, what does EGR do, and what would happen if I were to buy one of those block off plates? What else would I have to do after blocking it off?

Grim Reaper

The EGR basically takes "inert" exhaust gas and includes it with the "fresh" incoming air. By decreasing the amount of "fresh" air, it effectively does the same thing as decreasing the displacement of your motor. Thus it makes you burn less gasoline while cruising on the highway. Which reduces emissions since you have a less "reactive" mixture in the cylinder.

The diluted mixture also allows you to run a higher compression ratio while at part throttle, thus reducing your chance of detonation and allowing you use a higher spark advance. This gives you better gas mileage and less emissions too, especially NOx, which is caused by retarded timing.

The great thing, is that the EGR only functions at part throttle, when you want your engine to take advantage of these characteristics. The ecm does not allow it to function when the throttle is at 0% (idle or deceleration) or at 100% WOT.

I have a relocated MAT. When the ecm detects that the incoming air temperature is less than +5*C (about 44*F), the EGR ceases to function. This causes my gas mileage to greatly decrease during winter driving and why I reconnect the stock MAT during winter.

[This message has been edited by Glenn91L98GTA (edited February 03, 2001).]

90Iroc

Thans Glenn, you wouldn't happen to have a picture of that relocated MAT would you? How much did you spend to do that? TPIS makes a kit for that, but I can't remember off hand how much it was. So it makes a definite improvement? SOTP improvement, or just noticeable in gas milage? What do you think of the TPS voltage enhancer?

GTA91

iTrader: (1)

EGR huh? I think thats what is wrong with my car. It does that stumbling crap all the time off and on. Different times, different throttle applications, but really does at low speeds and when i go to shift into 2nd(5-spd) It also seems to do it on hills or when the motor is in a bind. I also noticed that it quits if i floor the gas or push the clutch in, otherwise it does a horrifying stumbling/dying maneuver. Well, I'll definatley replace the EGR when I put the 350 in. I guess I'll hold off on those new IAc, TPS, and MAP. I figured they needed replaced anyways with 143k miles. BTW- Are WELLS products any good? Later... thanks for the help!

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'91 GTA:
www.fbody.com/members/91WS6GTA

90Iroc

Yup EGR it sounds like. I'm going to replace it tomorrow. I went and got the EGR and upper plenum gaskets today. My car also quits when I push in the clutch or floor it. Well here's the thing, if it's the EGR screwing up, why is there no code being set?

86Trans Am

MIne had the same type of hesitation/jerking at low speeds and right after the upshifts, once in awhile it was hard to start. Then one day at a stop light it jerked, bucked, and missed out and then died, wouldn;t restart. FUEL PUMP.

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1986 Trans Am
305 TPI
"If it's not one thing, it's another!"
http://www2.hanover.edu/hierlmeier

Grim Reaper

Yes, a "weak" fuel pump can also do it, along with a clogged fuel filter. But it tends to do it at ALL rpms, not at the lower part.

Dying fuel pumps are funny. I have heard a few people say they got the same "sign" as you did. Conversley, I got absolutely no sign. My car was running great the day before, and then I went to start it and I got nothing. The first thing I did was listen for the old familiar "2 second hum when I turned on the key" and noticed nothing.

But yes, "fuel starvation" due to a "weak" fuel pump or clogged fuel filter can also cause it, especially if it is at ALL rpms in ALL gears.

90Iroc

Okay, the EGR seems to be okay, I checked it, I pulled it off the intake and I pushed in the diaphram and it help in place while I put my finger over the little hole. The jerking is at about 1500 RPM's and then if I accelerate at any time to 3000 RPM's, once it gets to or surpasses the 3000 mark it acts like a misfire. I can tell by the sound and feel that it's losing power. When it does that though, if I mash on the gas it's fine. What does the EGR solenoid do? Last year I broke one of the vacuum lines and repaired it with super glue. Do you think that maybe that's come un-done and is causing this? I don't know what that solenoid does. But it was fixed. I guess I'll have to check that this weekend.

Grim Reaper

The solenoid is the part controlled by the computer. That part is often a problem too.

burnoutrpm

talk to "the odb" he's cool!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 160 (882) heads,.447/.447 lift 222@.050 duration speed pro 327/350hp cam 350 .40 over (356) Edlebrock torker2 and a 600 edlebrock manual choke (1405)

Future mods performer rpm air gap intake (polished) comp roller cam, and way better headsa 400 defintely in the works!

burnoutrpm

but anyhow it sounds like the msd box they have been known to do that sort of thing my frined has it no his s-10 and he cured it by changing his springs but first tried the rubber grommets and it helped greatly! so id get the rubber grommets first always start with the cheapest thing first! then get more expensive and pray and deny the exspensive thing isn't it!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 160 (882) heads,.447/.447 lift 222@.050 duration speed pro 327/350hp cam 350 .40 over (356) Edlebrock torker2 and a 600 edlebrock manual choke (1405)

Future mods performer rpm air gap intake (polished) comp roller cam, and way better headsa 400 defintely in the works!

90Iroc

So the suspension was causing his problems? I'll go to the hardware store too and get some grommets for the box. I'd better tell my brother too!