Losing my grip


#1

I have a 91 Maxima that has a very strange problem going on - too much to get into here i think. After taking it to several reputable mechanics including the dealer - none of whom could figure out what was going on - I let it sit for 9 months. Last week I took it back into a well respected shop and they said they found the problem - a warped exhaust manifold caused by some broken studs. This was causing a miss on two cynlinders (#3 & #5). I paid them $1058.06 for the work they did and drove it to work. On my way home from work it dies again and displays the same symptoms it did before I took it in. They have said to bring it back and I am wondering how I should approach them. I cannot afford to pay that money to have it not work - I had to practically deplete our savings to pay the bill to begin with. I feely they desreve money for the work they did, but then they didn;t fix my car so I also feel like they don;t deserve anything and I should dispute the payment. your advice?


#2

You’re jumping the gun here…Bring it back to them and let them look at it first. IF they say it’s NOW problem B after you already paid for problem A…THEN I’d start negotiating on getting most if not ALL my money back on the first job. It could be a simple fix and they’ll have it right with no cost to you soon.

With all that said…I have to say I’m a little skeptical of thier first fix. 90 - 94 Nissan 3.0l engines had a problem with the exhaust manifold. However the ONLY symptons would be the exhaust a little louder and you MIGHT smell some exhaust. Never heard of this problem causing a missfire. If the vehicle was truely missfiring then I suspect it’s NOT the exhaust manifold…It may have been bad…but I don’t think it caused the missfiring.

Second…Did they actually REPLACE the manifold…or just the gasket. If just the gasket the old manifold needs to be checked for warpage and if not either replace or machine it to fit correctly.


#3

I know I am a bit ahead of myself and I will see what they say. This has just been such a frustrating run to get this problem fixed and we have nickle and dimed our way up to about 3x the value of the car trying to repair it.

They actually put on a new manifold and gasket.


#4

I don’t know what the other mechanics may, or may not, have done; but, (besides a long lists of tests) I would suspect the intake manifold gasket of leaking vacuum at #3 and #5 cylinders. #2 is in between those, and it’s not misfiring. #3 and #5 intakes are at the ends of the intake manifold. What MIGHT help such a vacuum leak is loosening and re-tightening the RH intake manifold bolts. Do an engine test run. If it still misfires (can YOU detect it misfiring?), get RTV sealant, from an auto parts store, and smear it all around the intake manifold to cylinder head joint. A mechanically inclined (some would say, “bent”) acquaintance could do this for you. The Haynes manual would have to be checked for turning off the eheck engine light.


#5

A warped exhaust manifold may cause a leak which will be noisy and irritating but it is not going to cause an engine performance problem or engine miss.

Since the alleged problem cylinders are adjacent to each other this could point to a head gasket problem, or either an ignition miss.
Even a misfiring spark plug could do it since the spark is going to go somewhere; either to another plug wire or another terminal inside of the distributor cap.

In a shop setting, and given your complaint(how many miles on the car?) step no. 1 should be running a compression test and ruling out a mechanical fault.

There is not a misunderstanding about which manifold had the problem is it? An exhaust manifold will not cause this problem, but a leaking intake manifold could.


#6

The car has 136,000 miles on it. The problem I have experienced is a lot like a misfire issue. The car runs GREAT when the engine is cold, but as it wamrs up it begins to fail (chug and stutter) at 3000rpm, then around 1800rpm - evetually it just refuses to move forward - killed it three times trying to move one car length.

Have had the valves replaced, new alternator, nw master cylinder, now a new exhaust manifold and gasket, new distributor cap and wiring harness, new plugs and plug wires. All of these were diagnoses from mechanics and their ideas for repair.

I will try some of the things you have suggested here and hope for the best :-).


#7

Disconnect the vacuum control hose/electrical connector to the egr valve and the charcoal canister purge control valve. If they are opening too early, or too much, they can make the engine run lean.


#8

With the new info, my feeling is that the problem is not related to a head gasket problem or an air leak. Generally an air leak will cause a rough running engine when it is cold.

You might consider the possibility of a failing fuel pump. Pumps can start off fine and gradually start failing after running a while. The symptoms can vary from cutting out to flat out stalling; e.g., barely moving even with the pedal on the floor.

If the fuel filter has been replaced and the old one was partially clogged then this could kill a pump. Whenever changing a filter I always dump the contents into a jar, examine it, and test the filter for blockage.

About a year ago my daughter was complaining of something like this on one of her cars. It was stalling on an erratic basis.
She left it with me as a daily driver and I drove it for over a week with not a hiccup. Took a 200 mile road trip and sure enough, about 20 miles from the house on the way back (and on a 100 degree day of course) it acted up in the way you mention.
At least I verified the problem (pump)! Sat for half an hour, it started up and ran fine all the way home.
Changed the pump the next morning and fine ever since.