Hesitant Acceleration
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From: austin
Hesitant Acceleration
'90 3.0L has a hesitant accerlation, will almost die when giving it some gas but then catches up. Spews heavy amount of black smoke and soot on hard acceleration. Hard starting when it is hot, starts fine when cold. Finally, all the sensors show up when reading codes on the van. New plugs, wires, rotor, rotor cap, oxygen sensor, and pcv. Oil is ok, water is ok. Any ideas what to consider first greatly appreciated.
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From: cincinnati hamilton
the first thing i would do is check for deposits around your butterfly valve on the air intake throat of the throttle body. (take off the air inlet tube where it attaches to the engine) mine accumulates brownish deposits around the butterfly valve,they gum up the operation of the valve. they can be cleaned with a throttle body spray cleaner. this seems to help mine run smoother. if it doesn't help, at least you can rule it out. rick
91 aerostar xl, ext 4.0 litre
188 thousand miles and going....
91 aerostar xl, ext 4.0 litre
188 thousand miles and going....
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From: Surrey, BC Canada
This may sound whack, but by any chance could someone have accidently put diesel into your tank? It happens.
Same symtoms happened to me many years ago with a different vehicle. The kid in the gas station thought it took diesel. OOps.
Smell your tank, if they did dont worry to much, better to have diesel in a gas engine then gas in a diesel.
Good Luck
Andrew, Surrey BC
Same symtoms happened to me many years ago with a different vehicle. The kid in the gas station thought it took diesel. OOps.
Smell your tank, if they did dont worry to much, better to have diesel in a gas engine then gas in a diesel.
Good Luck
Andrew, Surrey BC
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From: PNW
Even if you see no gas in the vacuum line for the pressure regulator, it would be worthwhile to check the fuel pressure. It could be possible that the requlator failed such that the pressure is too high.
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From: austin
Replaced fuel pressure regulator
Finally got the fuel pressure regulator replaced (if I could only meet the guy who designed that bracket with the upside down bolts...). There was fuel in the vacuum port of the old one. The results are that I am not getting the sooty exhaust on the hard revving, but the hesitation is still there. In fact, the van now dies after a running for a short time.
I suspect that I may have clogged up the catalytic converters and am not getting good flow of the exhaust. Is this possible and is there any way to check it?
I suspect that I may have clogged up the catalytic converters and am not getting good flow of the exhaust. Is this possible and is there any way to check it?
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From: PNW
Before looking at the cat, check your plugs. If the engine has been running rich enough to make sooty exhaust, there's a good chance the plugs are dirty.
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My exhaust was restricted after having driven 1000km with a kinked fuel return hose -- very rich! Had back pressure tested for free at my local Minute Muffler shop. They are a very reputable dealer locally here.
If you can't do that then pull your o2 sensor and drive without it for a while.
Acheck for bad cats is rattling exhaust. Sometimes the heat shield on the muffler rattles but the cats also rattle as they age. Use a hose as a stethoscope on the cats.
A sure sign of bad cats is minor surging up a steep incline at about 40km per hour.
Another way to test is an intake vacuum test. Search the net for restricted exhaust and catalytic convertors.
If you can't do that then pull your o2 sensor and drive without it for a while.
Acheck for bad cats is rattling exhaust. Sometimes the heat shield on the muffler rattles but the cats also rattle as they age. Use a hose as a stethoscope on the cats.
A sure sign of bad cats is minor surging up a steep incline at about 40km per hour.
Another way to test is an intake vacuum test. Search the net for restricted exhaust and catalytic convertors.
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EXHAUST BACK PRESSURE
Starting with the engine at idle, slowly increase engine speed to 3000 RPM, engine vacuum should be equal to or higher than idle vacuum at 3000 RPM.
If vacuum decreases at higher engine RPM's, an excessive exhaust back pressure is probably present.
(from alldata)
Starting with the engine at idle, slowly increase engine speed to 3000 RPM, engine vacuum should be equal to or higher than idle vacuum at 3000 RPM.
If vacuum decreases at higher engine RPM's, an excessive exhaust back pressure is probably present.
(from alldata)