Troubleshooting question
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From: barre usa
Troubleshooting question
[updated:LAST EDITED ON 23-Feb-02 AT 01:28 PM (EST)]I gave up trying to figure out why my 92 Bronco 302 runs rough when cold and stalls when I come to a stop when warm. I brought it to a local mechanic and he did a compression test (thinking I had a bad valve) The test came up 150 lbs on all cylinders! Not bad for 132,000 miles.
He said he thinks it is a leaking intake gasket. The job will take about 6 hours. I dont feel confident with it but that is what he thinks.
I did pull the codes before I gave it to him. One code said the right bank is running rich.
What do you guys think?
Jon
He said he thinks it is a leaking intake gasket. The job will take about 6 hours. I dont feel confident with it but that is what he thinks.
I did pull the codes before I gave it to him. One code said the right bank is running rich.
What do you guys think?
Jon
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Troubleshooting question
Get another opinion....my personal observation is that when a mechanic states "I think it might be..." then the mechanic might as well just guess.
If the mechanic spends 6 hours replacing gaskets and the problem is still there I will bet money that the mechanic tells you that the gaskets were bad anyway!
My advice is not to let ANYONE guess at your expense. How many gaskets and sensors will be guessed as bad?
Get the second opinion and do it right the first time.
Bob
If the mechanic spends 6 hours replacing gaskets and the problem is still there I will bet money that the mechanic tells you that the gaskets were bad anyway!
My advice is not to let ANYONE guess at your expense. How many gaskets and sensors will be guessed as bad?
Get the second opinion and do it right the first time.
Bob
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From: Carhenge
Troubleshooting question
Had the same sort of symptoms on my 91 a couple of years ago. It acted like a flooded carburated engine and got progressively worse-hard start, stalling when hot, blowing black smoke. I beat my head against the wall for a month trying to figure it out. Turns out it was the fuel pressure regulator. It is a vacuum operated diaphram regulator, the diaphram was leaking fuel through into the vacuum line (which was straight off the upper intake mainfold), causing the engine to run rich and stall. It is easy to check, pull the vacuum line off the regulator, if you smell gas you have a problem.
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From: barre usa
Troubleshooting question
He did put a vacume tester on and the vacume was all over the place.
He also checked the fuel pressure and it was right on spec.
The truck was running so rich it would burn your eyes!!
Jon
He also checked the fuel pressure and it was right on spec.
The truck was running so rich it would burn your eyes!!
Jon
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From: Virginia
Troubleshooting question
The mechanic might want to verify the following sensors before he checks the gaskets:
Engine temp sensor(measures coolant temp) at 194 degrees it should be about 2800 ohms and send back about .6 volts
Air charge temp sensor(measures air intake temp)-should be about 24,000 ohms at 86 degrees and should send back a voltage of about 2.6 volts.
He should have a chart that gives him more values than I have on here. If these sensors think the engine is cold, they will richen the mixture like a choke does, only they will do it all the time if they are broke.
One other thing my fuel injection book says it could be is the charcoal canister system. Apparently it can get flooded with fuel and cause the engine to run rich.
If it's nothing obvious like the previous examples, a vacuum leak in the intake manifold is a legitimate cause for the problem, but it is still a guess. Oh well.
Engine temp sensor(measures coolant temp) at 194 degrees it should be about 2800 ohms and send back about .6 volts
Air charge temp sensor(measures air intake temp)-should be about 24,000 ohms at 86 degrees and should send back a voltage of about 2.6 volts.
He should have a chart that gives him more values than I have on here. If these sensors think the engine is cold, they will richen the mixture like a choke does, only they will do it all the time if they are broke.
One other thing my fuel injection book says it could be is the charcoal canister system. Apparently it can get flooded with fuel and cause the engine to run rich.
If it's nothing obvious like the previous examples, a vacuum leak in the intake manifold is a legitimate cause for the problem, but it is still a guess. Oh well.
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Troubleshooting question
If it's any help: I had a similar problem w/ my '91 EB. changed the plugs, wires, PCV,and then bought a handheld code reader. Well, the EGR valve was the culprit! Cost me about $40 at AutoBarn and has run fine ever since. Good luck!
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From: webster city u.s.a
Troubleshooting question
I would check the O2 sensor operation. There is two O2 sensors one for each bank. the voltage should fluctuate from .02 to almost 1 volt and back down very quickly. It sounds like the right upstream O2 sensor is not switching.
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Troubleshooting question
The o2 sensor just reads the o2 in the exhaust,the reason it switches back and forth from low to high voltage is the computer is trying to adjust the ratio and it cycles from lean to rich.So if the computer is in open loop because of a bad sensor it may not cycle.I replaced mine with a new sensor and it stays at about .8 which is way rich.It doesn't cycle.Something is keeping the pcm in open loop.I have checked every sensor and had a mechanic do the same.I'm about to replace the pcm,other than a wiring problem I don't know what else it could be.
Billy
Billy
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