idle rough, hesitation when reving up
08-08-2008, 11:56 PM
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idle rough, hesitation when reving up
Rough idle and when you give it gas it stumbles and is down on power, but will rev up. I have drained the fuel and replaced with new, changed the fuel filter, fuel pump, spark plugs, wires and cap. I cleaned the throttle body and set the tps to .54v. Fuel pressure is good at idle and under load. Air cleaner is clean and maf seems clean. No codes I checked. Everything seems to be pluged in and has good vacuum. ohm on all the injectors is right in spec. Seems to be running alittle rich so I am thinking its electrical, but don't know. There has to be something silly I am missing. Could it be the ESC, Ignition module or coil going bad? Thanks for any help
08-08-2008, 11:59 PM
#2
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Rough idle and when you give it gas it stumbles and is down on power, but will rev up. I have drained the fuel and replaced with new, changed the fuel filter, fuel pump, spark plugs, wires and cap. I cleaned the throttle body and set the tps to .54v. Fuel pressure is good at idle and under load. Air cleaner is clean and maf seems clean. No codes I checked. Everything seems to be pluged in and has good vacuum. ohm on all the injectors is right in spec. Seems to be running alittle rich so I am thinking its electrical, but don't know. There has to be something silly I am missing. Could it be the ESC, Ignition module or coil going bad? Thanks for any help
08-09-2008, 01:48 PM
#6
Melting Slicks
Miles, throwing parts at a car is usually a bad idea, but how about changing the coolant temperature sensor, its only $16 at autozone.
Your problem sounds very much like mine, I still haven't figured it out.
Your problem sounds very much like mine, I still haven't figured it out.
08-09-2008, 02:43 PM
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"throwing parts at a car is usually a bad idea"
Not when the parts are 20+ years old. I threw all new parts at my 84 and it runs like a dream now. Parts can be marginal and still pass the testing at autozone or never trip a code, but as soon as they get hot or have a little amperage pumped through them they start intermittently failing.
Modules and fuel pumps are the worst, but IACs can get pretty weird too.
Not when the parts are 20+ years old. I threw all new parts at my 84 and it runs like a dream now. Parts can be marginal and still pass the testing at autozone or never trip a code, but as soon as they get hot or have a little amperage pumped through them they start intermittently failing.
Modules and fuel pumps are the worst, but IACs can get pretty weird too.
08-09-2008, 02:47 PM
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Could it be the ESC, Ignition module or coil going bad?
Coils can arc internally, giving you a stumble or a miss. The ESC will just retard your timing, and the module will completely fail and provide no spark at all.
I'd put in a MSD coil and replace the module with an accel since you'll be in the area.
Coils can arc internally, giving you a stumble or a miss. The ESC will just retard your timing, and the module will completely fail and provide no spark at all.
I'd put in a MSD coil and replace the module with an accel since you'll be in the area.
08-09-2008, 03:00 PM
#10
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The coolant temp sensor (not the one for the dash) tells the computer what the engine's temp. is. The computer adjusts the fuel sent based on those readings. When the sensor fails, it will tell the computer that it is -40F and cause the ecm to send way too much fuel.
08-09-2008, 03:10 PM
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Oh ok, is there a way to test the sensor tho? and if the sensor goes bad shouldn't it set off a code 14 or 15? and thanks for the help here guys. I know when I find the problem it will be something easy I just overlooked, I'm hoping
Last edited by MilesHenry; 08-09-2008 at 03:15 PM. Reason: added more info
08-09-2008, 03:23 PM
#12
Melting Slicks
It normally sets a code, but I've heard of cases where it didn't.
You can test the sensor by taking it out and puting the end of it in ~200F water. Then use an ohm meter to check the resistance.
It should look like this:
degrees F | Ohms
------------------------------------
210 | 185
160 | 450
100 | 1,600
70 | 3,400
40 | 7,500
20 | 13,500
0 | 25,000
But you could just buy a new one for $16 and save yourself the trouble.
You can test the sensor by taking it out and puting the end of it in ~200F water. Then use an ohm meter to check the resistance.
It should look like this:
degrees F | Ohms
------------------------------------
210 | 185
160 | 450
100 | 1,600
70 | 3,400
40 | 7,500
20 | 13,500
0 | 25,000
But you could just buy a new one for $16 and save yourself the trouble.
08-09-2008, 04:06 PM
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Ok there are 2 sensors right next to eachother on the front of the manifold. What one is the coolant sensor, one is bigger then the other. The bigger one has the fuel injector style wiring harnes. The smaller one is right under the cooland passage. Thanks again guys...
08-09-2008, 05:55 PM
#16
Melting Slicks
Well, atleast you know its good. 
Like I said, I've been battling the same type of problem for 5 months now and haven't got it figured out. Try unplugging the MAF when its cold and see if it idles better. Mine did, so I'm replacing the MAF, I'll let you know how that goes.
Like I said, I've been battling the same type of problem for 5 months now and haven't got it figured out. Try unplugging the MAF when its cold and see if it idles better. Mine did, so I'm replacing the MAF, I'll let you know how that goes.
08-09-2008, 09:32 PM
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I have the origional maf descreened. I shot some electrical cleaner at the wire, let it dry and it seemed to be alittle snappier but still not right. Could it be going bad and still not set off a code? is there a way to check the maf? Thanks,
08-09-2008, 09:49 PM
#18
Melting Slicks
I have a modified MAF from tpis right now. I cleaned it but got no results. I should have my new one monday, I'll let you know what happens.
Have you tried disconnecting it then firing it up?
Have you tried disconnecting it then firing it up?