Miss at idle.

[RustedRanger]

I have replaced a bunch of parts including the FPR which did the most good. I replaced the plugs 3 times now but the third time was before I replaced the FPR and I'm wondering if I fouled them out again. It idles down to 900-950 but has a miss/stumble,it's not real bad and the tach needle does'nt even jump but it still bugs me. It also idles high until it's all the way warmed up. When I first got it I messed up and lowered the idle by using the screw to set the TPS. I reset it but it would only go down to 1 volt,could that be the problem?

 

[holyford86]

pull codes

 

[RustedRanger]

Okay......no codes. The place I took it to before I changed the FPR looked for four hours and couldn't find anything either,he checked all the grounds and vacume line ect. and so have I. I think the FPR just didn't fail when they had it. I pulled the back two plugs and the insulators are white but I could tell they had gotten dirty before I ran Seafoam through it and changed the FPR. The pass side rear plug did have a little bit of a gas smell but I think the plug wire wasn't all the way on from where a place fixed the exhaust and had to burn the bolts out of the pass side manifold(he may have removed it). Also on start up it has a gas smell until it runs a second. Also since I changed the FPR when you start it cold it revs up like normal and dies,it didn't do that before and doesn't do it after the first start. I forgot it does give code 11 so the computer is working

 

[IMenriched]

has a compression check been done?

or vacuum gauge readings?

 

[AllanD]

I have replaced a bunch of parts including the FPR which did the most good. I replaced the plugs 3 times now but the third time was before I replaced the FPR and I'm wondering if I fouled them out again. It idles down to 900-950 but has a miss/stumble,it's not real bad and the tach needle does'nt even jump but it still bugs me. It also idles high until it's all the way warmed up. When I first got it I messed up and lowered the idle by using the screw to set the TPS. I reset it but it would only go down to 1 volt,could that be the problem?

the Tach is driven by the "primary circuit" side of the ignition system
a "miss" is the cylinder itself not firing for whatever reason...

You mention you changed the plugs three times...

How about the wires?

Distributor cap?

AD

 

[RustedRanger]

I have changed the cap,rotor,wires,PCV valve,IAC,FPR,CTS,TFI mod,IDM resistor,air filter,fuel filter and set the timing. No I havent checked the vacume or compression. I called a friend who does computer diagnostics said it could be a valve but doesnt seem like a bad sensor but could also be something in the wiring. I went back and checked the email the shop who checked it out sent me and they said when they had it the fuel pressure was 28psi running and said that was within spec but on here the guys say 40 KOEO and minus 3 to 6 psi running. I want to check the fuel pressure today and see what it is with the new FPR. The insulators on the plugs I checked were bright white but they still had some carbon(not alot) on the metal part of the plug. It didnt seem to have a miss like this until I changed the FPR,the idle just jumped up and down once warmed up but smooth and steady with it cold. Thanks for the info and help.

 

[Nailzs]

these engines were known for cahcking heads and blowing headgaskets...hows your coolant level doin? added any recently?

my 88 ranger had a flat out dead cylinder at idle cause it burned so much coolant

 

[RustedRanger]

I checked the fuel pressure today and its 40 KOEO and 31 at idle. I did like my friend told me and used carb cleaner and a rag to wipe out the throttle body even though I had already cleaned it once. Using the rag and getting to some of the back of the throttle plate helped alot and it had a ton of black junk on it. I made sure all the bolts on the intake/throttle body were tight. Then I went and got new Motorcraft plugs and put em in. Now it doesn't miss but just has a little bit of a stumble in the idle every 3 or 4 seconds. Otherwise it runs really good and what I did today did helped because I kept speeding on the way home. (less pedal to go the same speed) I did have to put some coolant in it recently but the clutch on the fan was bad and I didn't realize it until it got up to around 80 outside and the upper hose was leaking a little. But otherwise no white smoke out of the tailpipe and the plugs all looked about the same. Also no sign of water in the oil or milky residue under the filler cap or bubbles in the coolant while running. Thanks again for all the advice

 

[RustedRanger]

OK.....I thought I had it fixed...... I have driven it several times now and each time the stumble at idle is getting worse each time I drive it and now it has gas in the oil again. I have changed it 4 times now in about 3 months/1500 mi. Its stumbling enough that you can see the motor shake and now it's doing it off idle coming down our lane. Coolant is still full and circulating and no bubbles,still running cool. It doesn't smoke at all,it leaks oil from the valve covers and main seal but it doesn't get low quick and I never let it get lower than maybe half a quart. I'm having my friend that does mobile diagnostics come to check it tomorrow. I'm hoping and praying it is not something wrong internaly with the engine. I drive easy and don't beat on it but I don't lug it either. Thanks y'all.

 

[RustedRanger]

My friend checked out the Ranger today. He found that the sensors are working fine and that the engine itself is ok. He was looking for a wire to test the O2 sensor in the harness so it'd be easier to get to and found a really bad ground wire in the plug-ins on the drivers side wheel well. He also noticed that the purge solenoid for the evap cannister is gone so it was drawing fuel vapor all the time. The line from the evap cannister was hooked directly to vacume on the throttle body. I don't know what the ground was for but couldn't have helped the way it ran and the purge solenoid could have been causing it to run rich. Of course when we started checking it today it ran much better than it did the last three times I drove it,I think because it has been sitting the last two days and there wasn't pressure built up in the tank from the fuel sloshing around. I'm gonna take it for a drive now and if I don't add to this post then it's fixed!
Thanks for the help and advice. BTW it does still have a slight stumble but he said that it runs better than most he has checked out and that the way it runs now is normal for its age and miles,it had around 15-16 inches of vacume and stayed steady,and God Bless him he didn't charge me anything and he usally charges $50. That ground wire broke off when he moved the plug in to check it,it was all green.