Throttle Body Problem, maybe
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From: Front Range of Colorado
Throttle Body Problem, maybe
Hi, my '89 Bronco 351W has been very sick. It runs very rich with a rough idle and acceleration. So far all sensors have been replaced, the distributor control modual, PCM, IAC, EGR stuff, relays (fuel and EEC) the engine harness rebuilt. Today I replaced the distributor cap and rotor and control module. It runs much smoother, getting rid of a misfire, but still idles rough and stumble or rough acceleration.
The question is when I took out the bottom screw of the IAC it was rusty. I would not think that it should be rusty from its location and none of the other fasteners near it showed water problems. Could that show an internal failure of the throttle body?
Thank you
Pam
The question is when I took out the bottom screw of the IAC it was rusty. I would not think that it should be rusty from its location and none of the other fasteners near it showed water problems. Could that show an internal failure of the throttle body?
Thank you
Pam
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From: Bend,OR
have you gotten the codes pulled yet? how about fuel filter change? when you replaced the cap/rotor did you change out the plugs and what kind did you use. also what is the timing set at. should be at 10*btdc with spout connector removed. did you replace the o2 sensor as well?
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From: Front Range of Colorado
There are no codes, the fuel filter was changed, new fuel pressure regulator, Motorcraft plugs have 75 miles on them, new Ford Racing 9mm wires, good spark on spark tester at the plugs, timing is 10btdc, and 02 sensor is new. Also, injectors are new. Vacum is a needle width below 15psi, high altitude. I was just out driving to help the PCM get adjusted after having the battery disconnected and I saw "smoke" that looked like what comes out from a very rich mixture.
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From: Front Range of Colorado
The engine was rebuilt and has about 150 miles on it. The build is very good, blueprinted. Block bored .030 with torque plates, bore aligned, crank under ground to specs. Crane cam, ford racing roller rocker arms, new pushrods, heads rebuilt new crane springs, new valves, 3 angle seats.
The engine runs fine, just it runs rich, and has the rough idle and rough or stumble acceleration. Once steady cruising it is very smooth. Yes it is supposed to be a solid engine, and the 85mph speedo tends to be pegged occasionally.
And since everything is new and checks out to specs the only thing I can think of is the throttle body and that screw with the rusty threads possibly indicating the throttle body is failing. (it will be replace once my Bronco passes emissions testing) It has passed emissions 2 years ago with this setup, but now it runs rich.
Pam
The engine runs fine, just it runs rich, and has the rough idle and rough or stumble acceleration. Once steady cruising it is very smooth. Yes it is supposed to be a solid engine, and the 85mph speedo tends to be pegged occasionally.
And since everything is new and checks out to specs the only thing I can think of is the throttle body and that screw with the rusty threads possibly indicating the throttle body is failing. (it will be replace once my Bronco passes emissions testing) It has passed emissions 2 years ago with this setup, but now it runs rich.
Pam
Last edited by Pam's Red; Jul 30, 2004 at 04:53 PM. Reason: complete sentence
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Pam:
Welcome to my nightmare. If your Bronco is an '89 then is has a speed density computer system on it and speed density has real problems with engine components which change vacuum or the overall parameters which it measures. (Even a little bit of change which I found out the hard hard way) I notice you said "crane cam" and I'm thinking that the crane cam probably has different lobe lift and duration and lobe seperation from the stock cam. I hope your problem is not the same as mine but don't throw parts at it until you know what the cam specs are. Chances are, they won't run with speed density. (Without idle surge, "rich" condition, irregular lope, and misc other gremlins.) I had hell with my '93 all this last year and had to learn a crap load about Ford EFI. P.S. every TB I ever saw had a rusty screw in it. Don't adjust it there. And don't use regular carb cleaner. (Use TB cleaner) My 2 cents. Hope I'm wrong.
Trouble.
Welcome to my nightmare. If your Bronco is an '89 then is has a speed density computer system on it and speed density has real problems with engine components which change vacuum or the overall parameters which it measures. (Even a little bit of change which I found out the hard hard way) I notice you said "crane cam" and I'm thinking that the crane cam probably has different lobe lift and duration and lobe seperation from the stock cam. I hope your problem is not the same as mine but don't throw parts at it until you know what the cam specs are. Chances are, they won't run with speed density. (Without idle surge, "rich" condition, irregular lope, and misc other gremlins.) I had hell with my '93 all this last year and had to learn a crap load about Ford EFI. P.S. every TB I ever saw had a rusty screw in it. Don't adjust it there. And don't use regular carb cleaner. (Use TB cleaner) My 2 cents. Hope I'm wrong.
Trouble.
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From: Hanscom AFB, MA
Pam,
With the speed density system, your cam has to have a LSA of at least 112 degrees, or it won't work well without adjusting things big time. Also, did you test your TPS?
With the speed density system, your cam has to have a LSA of at least 112 degrees, or it won't work well without adjusting things big time. Also, did you test your TPS?
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From: Front Range of Colorado
It has been MAF converted using Ford Racing kit. It was running great for a year+, then after a few hours of highway driving I stopped at a store. Came out a few minutes later then it wouldn't start up easily, it was running very rich and stumbling. Since then I have rebuilt the engine, replaced everything I listed. The only thing that hasn't been rebuilt or replaced is the throttle body, upper and lower intakes and two valves of the air pump system. It still runs the same as it did when it died that day. Rich, rough idle, and rough or stumble acceleration.
Pam
Pam
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From: just outside of Phila.
I noticed that Blue'87GT asked if you checked you throttle position sensor, and that you said you haven't replaced you TB, which is where the TPS is located (at least on my '88 302). That thing played games with me for a long time, and was one of the last things I checked (still learning), but when I did, it ran fine.
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From: Front Range of Colorado
TPS has been replaced and adjusted several times to get it set right on. Same with MAP, IAT, Coolent sensor, EGR parts (including a new tube), all vacuum lines, ALL sensors and relays. That is every single one of them. The computer, the distributor ignition module, the cap rotor, adaptor, (I haven't replaced the guts because they work just fine in all tests) The coil, wires. The TAB, TAD, and EVR. The wiring harnesses have been either replaced or rebuilt. The IAC, the purge solenoid, and the alternator. And the O2 sensor twice.
The only thing I have not done is replace the throttle body, upper and lower intakes.
Pam
The only thing I have not done is replace the throttle body, upper and lower intakes.
Pam
Last edited by Pam's Red; Jul 31, 2004 at 09:27 AM. Reason: finish sentence
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From: Groton, CT
Possible gasket leak at the intake or TB. Take a bottle of window cleaner (do not use anything flammable or it could prove dangerous and misleading) and spray around the upper/lower intake junction. Then move around the lower intake mating area and finally around the TB. If the idle changes suddenly while you are doing this, then you have found your leak. Also check for any breaks/leaks in your intake tubing between the MAF Sensor and the TB.
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From: Front Range of Colorado
I have gone back in with the vacuum gage and find 7.5 psi coming out of the line to the TAD, TAB and EGR controller. Should this be engine vacuum? I know the vacuum goes from intake manifold to the vac can then distributed, but not sure if it is restricted down from 15psi for those solenoids. Does anybody have that info?
Thanks
Pam
Thanks
Pam
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From: Front Range of Colorado
I put a pic of my Bronco in the gallery so you can see why I spend so much time and money on it. It shows up in 1989 Bronco
I drove it and although it smoothed out, the question is still about the 7.5 psi at the TAD, TAB and EGR solenoids.
Pam
I drove it and although it smoothed out, the question is still about the 7.5 psi at the TAD, TAB and EGR solenoids.
Pam
Last edited by Pam's Red; Jul 31, 2004 at 06:57 PM. Reason: finish sentence
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From: Groton, CT
Another option is to take your Bronc to a reputable FORD dealer with a full diagnostic system (not just a portable computer). They typically charge about $75 for this service. The "big machine" makes your rig look like it is on life support once it is hooked up, and allows the tech to see every tiny detail of what your engine is doing. It will almost always find the source of those odd little gremlins that make us crazy. I had one of those weird problems and their machine figured out that #8 injector would fail every fifth cycle, replaced the injector, no more gremlin.