hit a bump, engine running rough
Thread Starter
Pro
Joined: Mar 2004
Posts: 553
Likes: 6
From: Northern VA
hit a bump, engine running rough
Hi all,
I had my 86 vert literally humming then I hit a pot hole last friday and the car suddenly started running rough like it's on 7 cylinders. This happened immediately upon hitting the damned pot hole. I quickly checked the plug wires and they all seem plugged in just fine. The distributor is not loose and the wires into the distributor are connected solid.
WTF? what else could cause this? Could an electrical component go bad after hitting a pothole?
Thanks
Lee
I had my 86 vert literally humming then I hit a pot hole last friday and the car suddenly started running rough like it's on 7 cylinders. This happened immediately upon hitting the damned pot hole. I quickly checked the plug wires and they all seem plugged in just fine. The distributor is not loose and the wires into the distributor are connected solid.
WTF? what else could cause this? Could an electrical component go bad after hitting a pothole?
Thanks
Lee
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Push on each injector connection to be sure the impact did not dislodge the electrical connector to the injector. If this does not solve your problem, remove each injector lead one at a time and see which lead (when removed) does not create a change in the idle. This will give you and indication that it is related to a cylinder or some other issue. Got to start somewhere and do the simple stuff first 
Last edited by Sam Lam; Oct 30, 2007 at 09:26 AM.
Thread Starter
Pro
Joined: Mar 2004
Posts: 553
Likes: 6
From: Northern VA
Thanks Sam. I'll try messing around with the inhector wires this weekend. I didn't think about that but is sounds very reasonable. Great picture of your kid (I assume) behind the wheel. Start em off early :-)
Le Mans Master
Joined: Mar 2006
Posts: 5,262
Likes: 0
From: E. Amherst NY
Feel down each of your plug wires. I had something very similar happen to me in my '86. Car was running great, came to a stop sign to make a right, made the right and it was instantly down on power.
Probably spent the better part of 3 hours troubleshooting -- plug wires were the first thing I checked, albeit not too well. Tested the injectors and everything else, came out fine. My neighbor who is also a car guy came over. He started like the plug wires and found one that had just barely rubbing on something. Swapped it out with a different wire and voila.
I felt like an idiot..
Probably spent the better part of 3 hours troubleshooting -- plug wires were the first thing I checked, albeit not too well. Tested the injectors and everything else, came out fine. My neighbor who is also a car guy came over. He started like the plug wires and found one that had just barely rubbing on something. Swapped it out with a different wire and voila.
I felt like an idiot..
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
While, as has been pointed ou in other threads, it is unlikely that bouncing
through a pot hole would cause the timing chain to skip a tooth or damage
a distributor, perhaps water at the bottom of the tank rose up into the
fuel pickup tray and was thus drawn into the fuel line.
Commercial products like those sold at service stations or BG Fuel System
Drier #280 are safe to try adding to the tank. I don't have any bottles
on hand to check whether isopropyl alcohol or methyl hydrate is the
current principal ingredient in these products but I have used both for
gas line antifreeze purposes. Isopropyl alcohol is available from pharmacies.
You do not need to add much. A couple of ounces in the tank will
make a difference if water in the injectors is actually the problem.
.
Racer
Joined: Oct 2006
Posts: 438
Likes: 14
From: Tucson/Santa Paula AZ/CA
2017 C4 of Year Finalist
C'mon over and I'll hook it up to my Diacom+ 
Sorry, VA is a long way from Tucson. 
It sure sounds 'dead' on that little video. Did you ever hook up a timing light to each plug wire? Might tell you which cylinder is failing.
Mick
Sorry, VA is a long way from Tucson. It sure sounds 'dead' on that little video. Did you ever hook up a timing light to each plug wire? Might tell you which cylinder is failing.
Mick
Last edited by QZRBLU; Dec 10, 2007 at 07:51 PM.
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
Make sure that all of the electrical connectors (weatherpacks) are in tight and none of their wires have pulled out. Our '91 broke an electrical weatherpack plug "keeper" (the plastic tab) such that the plug could slide out just enough to loose contact and put the car in "limp" mode.
Fri--in dealer took three hours to diagnose, but I refused to pay for more than one! They were swapping out parts while I kept saying "probe the computer," which they finally did and instantly saw the code.
Fri--in dealer took three hours to diagnose, but I refused to pay for more than one! They were swapping out parts while I kept saying "probe the computer," which they finally did and instantly saw the code.
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Thread Starter
Pro
Joined: Mar 2004
Posts: 553
Likes: 6
From: Northern VA
Hi All,
Thanks for everybody's help and advice.
so far, I tried unplugging then replugging each injector electrical wire one at a time while the car was running and the problem remained unchanged. Rough idle and shaking badly.
I listened to each injector while disconnecting and reconnecting the electrical leads and I could hear them clicking loudly when connected and silent when disconnected.
I replaced all plugs, plug wires, dist cap and rotor cap.
I put a timing light around each plug wire and got the light strobing on every one.
No codes at all.
I checked all electrical connections in the engine compartment, ie: maf, iac, mat. I even dropped the ECM from under the passenger dash footwell and checked all those connections.
I checked fuel pressure. 42 in key on and 39-40 when running. It held up to 30 psi 30 minutes later.
I retimed the engine to 6 degrees BTDC as the VECI label says.
no change. Hard start and needing to feather the gas pedal for several minutes until the engine warms up then it just idles somewhat roughly and shaks during idle.
http://www.labib.com/runningbad.wmv
I'll be lifting it to look underneath for something glaringly obvious and will be back to report. We had 3 inches of snow on the ground until yesterday so please forgive the lapses between postings.
Thanks
Lee
Thanks for everybody's help and advice.
so far, I tried unplugging then replugging each injector electrical wire one at a time while the car was running and the problem remained unchanged. Rough idle and shaking badly.
I listened to each injector while disconnecting and reconnecting the electrical leads and I could hear them clicking loudly when connected and silent when disconnected.
I replaced all plugs, plug wires, dist cap and rotor cap.
I put a timing light around each plug wire and got the light strobing on every one.
No codes at all.
I checked all electrical connections in the engine compartment, ie: maf, iac, mat. I even dropped the ECM from under the passenger dash footwell and checked all those connections.
I checked fuel pressure. 42 in key on and 39-40 when running. It held up to 30 psi 30 minutes later.
I retimed the engine to 6 degrees BTDC as the VECI label says.
no change. Hard start and needing to feather the gas pedal for several minutes until the engine warms up then it just idles somewhat roughly and shaks during idle.
http://www.labib.com/runningbad.wmv
I'll be lifting it to look underneath for something glaringly obvious and will be back to report. We had 3 inches of snow on the ground until yesterday so please forgive the lapses between postings.
Thanks
Lee
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I feel bad that you haven't found the problem yet but I feel even worse that you are working out in the cold. Does the car run well enough to get it to a garage where they can put it on a scanner? Maybe if you find which cylinder or cylinders are weak you can narrow your search. I just can't imagine what hitting a pothole could do to cause this, if that was the case my car would never run right with Illinois roads the way they are. Did you check the maf internally for broken wires?
Intermediate
Joined: Mar 2006
Posts: 35
Likes: 0
From: Belleville IL
This is going to sound dumb, the VERY same thing happened to me in my '98 Camaro. Have you Catalytic Converter checked out. I never replaced it I just beat on it a little with a rubber mallet. The best explanation I got was the bump knocked loose some of the cones inside the cat which blocked flow through the cat and caused the power lose and inability to idle.
Let me know if this helps.
Let me know if this helps.
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
This could very well be it, does the engine idle a bit higher now than it did? Check the vacuum ball up by the drivers side headlight and the master cylinder connection and even a possibly cracked brake booster. By the time you check all this you'll be too darned cold to do any more.
Drifting
Joined: Dec 2000
Posts: 1,833
Likes: 4
From: Calgary, Alberta
Since the rest isn't getting you anywhere.....In my '88, I hit a bump in the road and my Car almost died like it was running on 5 or 6 cylinders. As I pulled over I hit a small bump and the Car ran fine. Hit another and all the Dash lights turned on and Car died. I pulled the Computer behind the dash pad and started the Car, tapped the box and Car stalled. I also hooked it up to be scanned and there was no signal most of the time. I replaced the ECM with a "new" one from GM ($100 cdn). That was about 6 years ago and been fine ever since, something about the circuit board according to GM.
Race Director
Joined: Nov 2004
Posts: 14,176
Likes: 142
From: Central Il
It could even be something as simple as a fuel filter. The bump may have dis-lodged some crud from your tank.
If that's the case, you could probably still get the proper pressure to your rail, just not enough volume of fuel.
A filter is only $5 or $6 dollars and is cheap piece of mind.
If that's the case, you could probably still get the proper pressure to your rail, just not enough volume of fuel.
A filter is only $5 or $6 dollars and is cheap piece of mind.
Race Director
Joined: Jan 2006
Posts: 10,039
Likes: 0
From: CA
How did you check the MAF?Did you disconnect it while it was running rough?Did it make any difference?It sure sounds like a damaged MAF sensor,but it should throw a code,but maybe not.The unit is pretty delicate,is the tiny wire in it still intact?
