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1991 Ford E-150 Other - Engine
Question: Engine has a very fast idle. guess about 2800rpm.+/-
Have checked the following: Idle air by pass (cleaned and 9volt check) swapped out with another idle bypass no difference.Installed a new gasket. Throttle Position sensor checked out. Removed throttle plate body and checked, throttle plates are not bent and seat OK no gaps when closed. New gasket installed. Egr valve removed and checked with vacuum, works fine. Tested EGR valve positioner with scan tool OK. Engine vacuum holds at 20+ ". The original code on KonEoff was 31 No other codes. Reset with battery disconnected for 10 min. and now no codes only 1 - 1. Sprayed as best as posible Wd40 around intake, no difference in idle. Plugs likenew. Gave in bought &
Installed new EEC computer, idle slowed up a little dropped maybe 120 +/- Has computer contolled idle.
Idle set screw not a problem. Starts immediately, stops the same (no run on)smooth running. Looked for shorted wires in injector wiring harness, looks great shape. Can pull off the vac line to the MAP will almost die out and then speeds up even faster, and riches up mixture and produces black exhaust smoke. Have not pulled distributor or pulled the ign. control module, but usually if they go bad, no fire.
Throttle cable ok, What am I missing?
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Technican: You are on the right track.. when you pulled the MAP vac line and the RPM jumped that was what gave me the idea to look for vac leaks.. Look at the following locations.. by the AC evap core box, check behind the glove box (there are 2 vac lines there also). I would pull the vac lines from the intake one at a time and plug them .. see what happens.. let me know.
ps.. look for the leaks to be away from the engine.
Owner: Al, am not sure you got my reply so I'll abreviate and answer again. Did all you suggested, took off L vac lines one at a time and plugged, no change, thought that it might be a bad diaphram in the vac brake cyl. NO such luck. Resprayed no luck, Will try disconnecting A/c but think it has to be sucking air somewhere. Disconnected speed sensor at flywheel no change. what else??? David
Owner: You do have a problem... I have to be honest.. I am stumpted.. I am releasing this to others and wish you ... you have done everything I would have done. Al
Technican: Which engine? Did you plug the idle and egr passageways? Try SLOWLY cutting off the air supply to the throttle body. Does engine stall? Have you pinched off the large hose to the brake booster?
Owner: Something must be wrong with this website as I typed a long long explanation but apparently it didn't get thru on the {send} button. So rather than go thru all of that. In short
Every Vacuum line individually removed, tested and no change.
EGR IAC MAP Sensors removed tested (Each individually) replaced with another unit No change.
Throttle body removed throttle plates checked close tightly, cleaned unit, replaced New Gaskets for Throttle body, EGR, IAC.
WD-40 sprayed plenum and intake manifold, no rpm change.
Replaced EEC computer with a new unit. No change.
Vacuum canister checked ok.
Starts easily, no smoke, runs smooth no vibration, Vacuum holds steady at 20+ ".
Yes I checked everywhere for vac leaks none to be found.
Yes I tried to choke of the engine with my hand over the 2 inlet ports as best as room allows, it slows the engine but doesn't kill it. That says I got a leak somewhere from the inlets to the block, but save a blown gasket or a crack in the plenum or intake manifold I sure as hell cannot find it, and neither can the wd40. So something tells me before i do a teardown there might be something else. But What???
Technican: Have you tried using propane to isolate leak?
If the inlets are at least partially blocked during testing the source of the leak would be easier to recognize. If you would post your engine size we could do a search at a tech site. Perhaps your posts were to big?
Owner: Like I said, 2 of my replys never got thru, when I would click send I would get a timed out message and all my typing was lost. from now on I do a ctrl C and don't lose what I have typed. So again...
The vehicle is a 1991 Ford conversion E-150 Van with a 5.0 litre (302) V8 Auto Trans, with approx 130, 000 miles. Just purchased with the fast idle condition. Usually I can figure these out rather quickly, but this one is really testing one's patience. As abviouos there isn't a lot of room for easy access under the hood on this vehicle.
I have removed the air filter box and the 2 inlet pipes from the throttle inlet for access, and for all trials, but have on two occasions replaced everything just to make sure it wasn't caused by some minor thing. I have not totally blocked the inlets, just as much as I hand can do in limited space, after the engine has been started, but will try that on monday, I will make a wood plate to totally block & cover the inlets. and see if it quits. if it does I'll make a couple of small holes just enough to keep it running and then, I assume that you are suggesting the use of a propane torch, obviously not lit but let the propane flow around the plenum, intake and around the exterior of the throttle plate, to see where the ornery is getting it's air. David.
Technican: Your assumptions are correct on the propane. Some use a stethoscope to hear the air sucking.
email me if you wish:
Owner: I wasn't able to work on that vehicle today as others were more pressing, will try to get at it tomorrow afternoon, but did isolate out the EGR as the problem as I blocked the EGR inlet to the plenum with no major change to rpm. I am thinking that it may be a cracked plenum, As I completely plugged both air inlets and it didn't kill the engine. So it has a major air leak somewhere in the intake manifold or plenum, or I am going to patent this engine for underwater use as it needs no air to run..
Will try the gassing the dude, asap, and will get back with results. Thanks David.
Technican: I didn't find much. Just that the intake/plenum gaskets sometimes go. THis don't help you much I know. But just wondering how it's going.
I also ran across many complaints about tps,
and a couple references to throttle cable problems.
Hey, the engine with no air patent would be something.
Technican: Ran across a ford tech who said the plenum gasket gets sucked in on this engine.
Owner: John, The propane trick didn't work all that well, it did however find an exhaust manifold crack, and the resulting !! POOF !! did made short work of the search. Luckily the amount of propane was not a large amount as just got started, and the result was enough to jump start the mechanics motor. Took 29 minutes to climb back down from the rafters. Made a definative decision, not to use that in any enclosed van or on second thought, scrap that one alltogether.
**Will use water and kill the motor instead. **
I have decided to pull the plenum and go from there, if there are no visable cracks, or bad gaskets then I'll pressure check plenun and if ok, then off with the intake and check it all out and regasket everything with sealant. Oh yes, and the rt.side exhaust manifold gets replaced, just happen to have a couple of those off other 302's, that I found on my quick trip up thru the attic. Since they look alike so we will see. Who says being a mechanic isn't fun? Where else can you get such a adrenelin rush? David.
Technican: Sorry for recommendation. We are bound to find trouble every now and a again. I guess we shouldn't use anything flammable to check for leaks. But it usually saves time. Water can do damage, but is quick. Blocking everthing off and inducing regulated air pressure through a leak down tester with intake valve open, and soapy water will find leak quickly.. Or there are obvious other ways to pressurize or apply vacuum to the system. Made an error in trying to take the fast route. Let me know how you make out.
Owner: Your Ford Mechanic friend was correct.
The difficulty was with the intake manifold to plenum gasket, and to say it gets sucked in is an understatement. At least 40 percent of the gasket was gone, The remaining gasket (parts) were hard as a rock, and were cracked, and the metal pressure mating marks showed that the gasket had truly been either installed defectively, or had somehow slipped inward, or both. Anyway the parts store gaskets did not appeal to me so I made my own out of some 600 degree 1/32" sheet gasket material and sealed it with 600 degree intake manifold sealant. The problem is one that probably occurs quite often due to the hold down on the passenger side center holddown. There are a total of 6 bolts ( 3 per side), however the center rt side is a T40 cap screw type rather than a bolt head, and the milled slot .404 " provided thru the plenum is not large enough to put a 3/8" drive with a 3/8" t40. The space under the bend of the plenum does not allow sticking the t40 in from the underside and trying to fish the drive down to connect. So this bolt does not get the proper torque and the leak begins on this side. Everything appeared to be original, so I feel this was a factory defect. This bolt was not even snug. A weld of a cut off t40 to a old 3/8" drive with the sq. hd cut off, finally got the job done and torqued to specs. Did a blow - vacuum on the intake before reassembly. What that was was a 18" lg. 1/4" plastic air tube connected to blow gun @ 140 psi stuck down to the bottom of each inlet in the intake manifold and a good canister vacuum sucking over the rest of the intake maniford inlet for each of 8 inlets, didn't want any pcs of that hard gasket holding open a valve and causing another problem. Did get a few pcs of old gasket up out of the intake so that got the job done, except.. After everything back together, and rt side exhaust manifold replaced, and new plugs while everything was out and why not, and late night to finish, yes you guessed it, The beast idles like it should, but now have an exhaust leak somewhere. Didn't notice it until I put the doghouse back and took it for a 20 mile test drive, enough to set the new computer.
Maybe I'll get lucky and it will be a small hole in the crossover, well that's what mechanics do is dream right. Another day, have to get on to the other 97 That's quantity, not year. (no bs) Anyway I pressed the pay the last time, it showed up again, this time, so let me know if it didn't pay you, I'll punch it again or whatever.
Well we learned something new?? Have a great weekend.
David
Technican: 97 to go! You wouldn't have that kind of backlog without a strong customer base. Are you from a large city? Maybe time to add another bay or two if you can find good help.
Or raise your rates and retire early. But if you like your job, that's all that matters. Don't work to hard.
Owner: John,
The 97 to go are not customer cars, I own them, and I have a used car lot and own a bunch of turkeys. Overbought due to a deal that fell thru with a body shop that went out of business. Got stuck with a balance of 100+ G's of inventory needing repair. So I am trying to work my way out of the mess and it isn't doing well, probably won't make it. Am either going to crush 50+ or find a spot and think about a salvage yard. Have lost 60 G's so far, and am trying to salvage some of the balance remaining so as not to lose the next 100. Nobody said it was gonna be easy, and it surely isn't. Other folks at 70 are retired, I'm still pulling engines and trans, and doing body work, and painting etc. Hey it keeps me going if nothing else. Was good getting your input.
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