4.0L poor acceleration
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4.0L poor acceleration
have a 1992 exporer with a 4.0L got it home and noticed the acceleration is alright (other than not going above 2000 rpm) when slowly pressing accelerator but when i put my foot on it it boggs down and tries to stall.still nothing over 2000 rpm.tested the tps and the botem end of it seems fine but theres a dead spot about 3/4 turn.(it only goes 90 degrees)we took the sparkplus out and cleaned them.that seemed to help a bit.thought it might be bad gas so we replaced the fuel and fuel filter.tested fuel pressure that seems to be fine at 38psi.smells a little rich in the exahaust....MAF is fine.all vacum lines seem to be working fine.the fuel pressure regulator is a bit suspect.any ideas?help would be apreciated.(new air filter,fuel filter) service engine light went out after replacing the MAF sensor.no codes coming up now.
Lead Driver
Joined: Sep 2003
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From: SoCal
Does the fuel pressure go up when you pull the vacuum line off? Can you check the fuel pressure while accelerating under load?
The TPS is relatively cheap and easy to replace, so it would be worthwhile to just do it to see if that helps.
If these are OK, I am suspecting the ignition, especially since you are smelling gas out the exhaust. How did the spark plugs look? Are the plug wires in good condition? The other two suspect items here are the coil pack and its control module. I know they're pretty expensive items to get new, but it might be worth it to try some parts from the salvage yard.
The TPS is relatively cheap and easy to replace, so it would be worthwhile to just do it to see if that helps.
If these are OK, I am suspecting the ignition, especially since you are smelling gas out the exhaust. How did the spark plugs look? Are the plug wires in good condition? The other two suspect items here are the coil pack and its control module. I know they're pretty expensive items to get new, but it might be worth it to try some parts from the salvage yard.
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we suspected the ignition system as well.we pulled the plugs and cleaned them some were worse than others.we atributed that mostly to rotten gas.getting good spark now.(as far as one can tell with a visual inspection)pulled the tank and while trying to unhook the sending unit the conections broke clean off the senind unit(it was very rusty)ordered new pump and sending unit.if there was a pinhole leak in the sending unit output hose would the sucked in air cause our symptoms?while we were pressure testing (reved not under load) we were getting quite a bit of air comeing from the fuel rail.also after about 10 minutes of leaving the key off and checking fuel pressure from rail we have none whatsoever.shouldnt i be retaining some pressure?thank you for your reply.
Does the fuel pressure go up when you pull the vacuum line off? Can you check the fuel pressure while accelerating under load?
The TPS is relatively cheap and easy to replace, so it would be worthwhile to just do it to see if that helps.
If these are OK, I am suspecting the ignition, especially since you are smelling gas out the exhaust. How did the spark plugs look? Are the plug wires in good condition? The other two suspect items here are the coil pack and its control module. I know they're pretty expensive items to get new, but it might be worth it to try some parts from the salvage yard.
The TPS is relatively cheap and easy to replace, so it would be worthwhile to just do it to see if that helps.
If these are OK, I am suspecting the ignition, especially since you are smelling gas out the exhaust. How did the spark plugs look? Are the plug wires in good condition? The other two suspect items here are the coil pack and its control module. I know they're pretty expensive items to get new, but it might be worth it to try some parts from the salvage yard.
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dang...
just finished replacing fuel pump/sending unit they both seem to work fine.no air in fuel rail anymore but engine wont flash and its flooding the heck out of itself.am rethinking the tps.could it also be my coolant temp sensor?its dreching the cylinders.thanks
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hmmm......shes a puzzler
ok.so we replaced the tps...not the problim...replaced fuel pressure regulator and still wont start.unpluged the vacum line from the fpr and it started!but only for a sec.no vacum from that line.traced the line back to the output "tree" on the right hand side of the intake.no vacumm there....could this be the cause of my problim?also we took the MAF housing off the throttleboddy and tried the ol either trick "either she'l fire of she wont" and still would not flash up even though we have spark...might it be to weak?how would i test the ignition pack.....is it one peice or is there another little brain box that goes with it?gettin desperate any thoughts would help thanks.
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Joined: Sep 2003
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From: SoCal
Sorry, I haven't checked this list for a couple weeks.
Does the 1992 4 liter engine come with an EGR valve? My 1990 and 1991 models did not.
It sounds like you have a big vacuum leak somewhere; the vacuum line going to the fpr comes directly from the tree, which is fed directly by the intake manifold. One problem is if you been have trouble starting the engine for a while, it may be very flooded.
A new pump should hold pressure for at least 30 minutes after shut off. Can you put a pressure gauge onto the fuel rail? Since you now have a new pump, the pressure should hold if the rest of the fuel system is in order. If it leaks down too quickly, it could be the fpr, or the injectors.
The coil pack is controlled by the EDIS module, usually screwed to the side of the inner fender. You could pull the plugs out to see if they spark outside the engine. While you have them out, check to see if they're wet. If so, let them dry out before re-installing. I've actually resurrected heavily carboned plugs using a propane blow torch.
The engine will not run properly without the MAF sensor, so you shouldn't try to run that way.
Does the 1992 4 liter engine come with an EGR valve? My 1990 and 1991 models did not.
It sounds like you have a big vacuum leak somewhere; the vacuum line going to the fpr comes directly from the tree, which is fed directly by the intake manifold. One problem is if you been have trouble starting the engine for a while, it may be very flooded.
A new pump should hold pressure for at least 30 minutes after shut off. Can you put a pressure gauge onto the fuel rail? Since you now have a new pump, the pressure should hold if the rest of the fuel system is in order. If it leaks down too quickly, it could be the fpr, or the injectors.
The coil pack is controlled by the EDIS module, usually screwed to the side of the inner fender. You could pull the plugs out to see if they spark outside the engine. While you have them out, check to see if they're wet. If so, let them dry out before re-installing. I've actually resurrected heavily carboned plugs using a propane blow torch.
The engine will not run properly without the MAF sensor, so you shouldn't try to run that way.
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