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So! The nightmare continues. Fuel pump was replaced but we noticed the wiring harness was a little bit singed during replacement. We cleaned it up as best we could, buttoned it up, car was drivable albeit the miss was still obvious. Not more than a week later it died in front of the Chevy dealership here in town ironically enough. I had to walk 5 miles in the dark from the dealership back to my mother's house in the bitterly cold wind and rain. Good times!

Dealership looked at it, charged me $75 to tell me the fuel pump and distributor were bad. They wanted $1,800 to replace them both. I towed it from the dealership (another nightmare I won't go into) back to my mechanic, and we replaced the Opti (which ROYALLY pisses me off since the new one came with a cap & rotor that has to be used to protect the lifetime warranty it came with, so now the $200 MSD cap and rotor I bought in February lasted a whole 10 months and I can't use or return it). Not to mention Advance Auto tried to give me just the cap and rotor when I ordered the entire Opti, so that was a fun little conversation/battle at the counter. "Old" MSD cap and rotor and factory AC Delco Opti had ZERO signs of damage, leakage, zilch evidence of any problems whatsoever. Engine still missing with new Opti. Still no codes. And it won't stay running now, either. Ordered new fuel pump hanging assembly which includes new fuel pump (new fuel pump I installed is now not returnable, either), but part is stuck in Georgia due to "local operational disruption," meaning I won't be getting the part any time soon.

When this entire adventure began back in August I looked all over the engine compartment for any signs of trouble whatsoever. I found a wire running from the steering shaft main wiring harness up around the brake booster check valve, around the driver's side intake manifold, wrapped around the front of the intake around/above the TB to the passenger side intake, and connecting someplace beneath the home plate. This wire was covered in plastic loom. This wire was partially melted and exposed, and the plastic loom had gotten so hot it melted into a grotesque black booger-looking creature up near the brake booster check valve. One of the reasons I replaced that valve was because the mystery wire was melted at that location, I figured the factory brake booster check valve was leaking and it melted the wire by letting hot engine air vent onto it. I also thought replacing that valve would solve the miss. So I replaced the valve with a new AC Delco one, then duct-taped that wire up as good as I could, wrapped it in new loom, and thought nothing more of it. My mechanic asked me what the wire was when he noticed it was spliced into the distributor wiring harness. I told him I had no idea what it was but it was the wire I told him about finding all melted and such. He said it's probably what fried my Opti. Turns out it's a tach sensor wire for my Viper alarm/remote start system. The guys at Best Buy said to bring it back in and they'll fix it when I can get the car there. So that little mystery is solved, but it has nothing to do with the engine miss because we left that wire un-spliced and capped off on the new Opti harness, and I'm seriously hesitant about letting Best Buy "fix it" when we get the car running again.

Cannot tell you how frustrated (and flat BROKE) I am at this point. This car was/is my daily driver and I have been borrowing my mother's car for 3 months now. It's a good thing she's retired or I don't know what the hell I would do. I have a new ignition control module to try next if the fuel pump hanging assembly replacement doesn't work, and after that the GD MSD wires are coming off and new AC Delco's are going on.

Exasperated!
Any update?

I have the EXACT same issue with my 95 Wagon.

Misfires, pings, backfires at WOT and surges/lurches randomly at stop light with foot on brake.

FP is good. Program is good. No codes.

I have been throwing parts at it, double checking plug wires, etc.

No resolution.

Next is the brake booster check valve and the EVAP. Looking for intake leaks.

Here's my thread: http://www.impalassforum.com/vBulletin/showthread.php?t=1238426
 

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Lance

I see our other thread about your problem. Referring to post 200 in this where that poster said he found a break in one of the injector wires you also could have something like that going on "somewhere" in your wiring

Like finding a needle in a haystack

FWIW "my" needle in a haystack problem years ago, which caused problems similar to yours, was the brown wire of the 4 going into the top connector of the Opti was not crimped and the wire was intermittent. Dealership (car was under warranty at that time) replaced several Optis thinking that was the problem.

By chance one day while the car was running I started touching pulling on various wires and BINGO when I touched that wire the car immediately died. On closer inspection the wire was not crimped when, assume AC Delco or whoever made the 4 pin Opti harness for GM, was made.

The popping thing is a common "opti" failure signal so take a GOOD look at the Opti harness. It won't cost you anything to closely inspect it.....may not be your problem but passing on what mine was as post 200 did in this thread

good luck
 

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Fixed! I think...

New brake booster check valve did not resolve the issues.

Bypassed EVAP system at the TB.

Had several WOT runs without backfiring and pinging along with no surging at idle with foot on brake.

Checked EVAP hoses and canister again. Sprayed them all while idling and nothing changed. Pretty sure there are no leaks in the hoses and canister.

I think fuel fumes from the gas tank are being sucked directly into the intake rather than outside air through a break/crack in the EVAP system.

Replace vapor vent solenoid or vapor purge valve or both?
 

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I hope that I'm putting this post in the right place. So I've been having this problem with my 96 Impala with about 140,000 miles not wanting to move as it should when I hit the gas. It feels like it wants to cut off. I've been reading & reading & searching & reading to find out who has the same problems as me. I've checked & changed some of the vacuum hoses, cleaned the throttle body, Air pump delete, spark plugs, cleaned behind the coil to make sure that it had a good ground on the head. And it's still doing the same thing. So I went on an hook up the scan tool. It gave me a code for the #1 injector, egr, evap system. So I bough some new injectors @26lb which is stock from what I read and changed the Egr. I'm still getting a backfire from the intake to where it broke my stock box. Rough idle and when I give it gas it doesn't want to move. I have to gas it slowly when in first(t56) to get it to move. If I dump the gas to take off, it won't move and feels like it wants to cut off. I really need this fixed as it's driving me crazy right now.

Dwyck
 

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I still haven't resolved my issue either. It's back.

Dwcyk I did not see the opti on your list of things changed or checked.

May want to pull it and see if coolant and/or oil are in the opti and if the rotor is bad.

I'm going to pull all the opti again (oil leak) and the plugs and hopefully find something there because I am running out of stuff to check.
 

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Hey Lance, that was my next part to change. Yesterday when I was putting everything back together, I seen oil on the top of the opti and the bottom where you plug it in. But I really don't know where the oil is coming from. It's driving me crazy right now, cause I'm trying to get my upgrades together for the winter(inhouse stuff) before it gets to cold. I'll see if I could take it down tonight and get back at you.
 

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Hey Lance, that was my next part to change. Yesterday when I was putting everything back together, I seen oil on the top of the opti and the bottom where you plug it in. But I really don't know where the oil is coming from. It's driving me crazy right now, cause I'm trying to get my upgrades together for the winter(inhouse stuff) before it gets to cold. I'll see if I could take it down tonight and get back at you.
Did you change the timing cover seals for the WP and opti? That's where your oil leak is coming from most likely.
 

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Check the fuses in the small box along the passenger side it's a small square black one beside the the one that says about the cooling fans then ck the condition of the online fuel filter underneath the passenger side body rail the ck fuel pressure regulator beside/ over top of the egr valve. My 94 used to do the same and it was that fuse in the lil box next to the fire wall
 

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Thought I would share what I went through in case it helps someone. Car wouldn't catch when cranking over but would backfire. Tested the ICM at Oreilly and was bad so threw that and a coil on it still no go. This was outside in the middle of a snow storm and due to humidity I thought the cap might have condensation causing the misfire. So a heat gun on 250 degrees for 20 minutes and she starts up. Still has issues of not wanting to start when it's cold and keeps getting worse and water pump was leaking so go into the tear down. Cap and rotor looked really good with little wear but on the opti wheel was oil and it was scraping the sensor due to bearing wobble, car has 156k. Got my new Delphi opti, new water pump and went through every ground with a wire wheel to ensure all works. Buttoned it all up only cranks a second then starter disengages so go buy a new corvette GR starter and the car runs better than when I bought it. The point of all this is at high mileage too much cranking like an opti going out can cause more old parts to die. With the diagnostics page I was able to verify everything else functioning with a simple test light
 

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im having an issue with rough idle and jerking during low rpms while driving. the jerking will go away if I give a bit more throttle to it. my rough idle seems to smooth itself when the a/c is on. I have pulled the vacuum line to the fuel pressure regulator and there was no fuel coming out and the FPR was dry. I also sometimes have a hard time starting the car, it sometimes will turn over and instantly die or turn over sounds like it wants to die then come back to life and have a higher idle than normal then smooth out to normal. I can smell a heavy exhaust smell from the passenger side of the engine close to the cat. I have no CEL on, no other lights on. 94 4.3L
any ideas?:confused:
 

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Finally solved

Check your plug wires. Check them again. Then check them one more time.

If you do not see anything, get an extra set of eyes. I have been chasing this rough driving for so long that I over looked a burnt plug wire.
Nab found it even after I checked several times.

Also, my coil went bad and when it was replaced, discovered that the ICM was bad.

Do not buy a cheap coil and ICM. I have been through two cheap coils.

Ordered AC Delco coil and ICM.

If it isn't the opti and harness, then check them plug wires and ICM.
 

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Another fellow and now you, fixed with wires. "another set of eyes", "old parts make other parts fail", and "don't buy cheap parts" are golden rules of life eh.
 

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My car has started an issue where AFTER it is warm (Like coming back from shopping), when I go to start it- the RPM's dip into stalling territory then bounces back up to 1k, just to dip back down again. It'll do this for about 5 seconds before it finally stalls out. This will happen two times. On the third He fires up normally or I'm usually giving him some gas to stay up on it, then he's perfectly fine after that. Other than that he drives perfectly the rest of the time. Fires up cold perfectly. This only happens once or twice a month and only after I've driven it.

Guess it's time to go down that list.
 

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My car has started an issue where AFTER it is warm (Like coming back from shopping), when I go to start it- the RPM's dip into stalling territory then bounces back up to 1k, just to dip back down again. It'll do this for about 5 seconds before it finally stalls out. This will happen two times. On the third He fires up normally or I'm usually giving him some gas to stay up on it, then he's perfectly fine after that. Other than that he drives perfectly the rest of the time. Fires up cold perfectly. This only happens once or twice a month and only after I've driven it.

Guess it's time to go down that list.
Um, weren't you having exactly the same issue up there in your vid this time last year? Cold weather? - problem. Cold weather? - problem. Hmmmm

Hey, in addition to our own (superior) stickies there's no lack of other lists out there:

Symptom: The engine will not idle smoothly, or it stalls during idle when the engine is warm. When the engine is warm or hot and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine.

Possible causes:

There may be a vacuum leak.
The Fix: Check and replace vacuum lines as required.

The fuel pressure regulator may be operating at too low a pressure.
The Fix: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator.

Idle speed set incorrectly.
The Fix: Set idle speed to specs.

There may be some type of ignition problem.
The Fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.

There may be a fault in the computerized engine control system.
The Fix: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)

The EGR valve may be bad.
The Fix: Replace EGR valve.

The fuel injectors may be dirty.
The Fix: Clean or replace fuel injectors.

 

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My car has started an issue where AFTER it is warm (Like coming back from shopping), when I go to start it- the RPM's dip into stalling territory then bounces back up to 1k, just to dip back down again. It'll do this for about 5 seconds before it finally stalls out. This will happen two times. On the third He fires up normally or I'm usually giving him some gas to stay up on it, then he's perfectly fine after that. Other than that he drives perfectly the rest of the time. Fires up cold perfectly. This only happens once or twice a month and only after I've driven it.

Guess it's time to go down that list.
Check fuel pressure for a failing pump.
 

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Black, in the video the car would stall (or attempt to) when driving around at idle in slow speeds. A new Idle Air Control Valve solved that issue, although I did replace the EGR as well.

This one just happens on start of a warm engine.
 
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