North American Turbocoupe Organization



Engine miss - Tried the usual
Wittsend Offline
Junior Member
#1
I have a '88, 5 speed. I have a slight intermittent miss at idle that increases significantly from about 2,000 to 4,500 RPM. After 4,500 RPM I'm not sure if the engine is turning too fast to detect the miss, but I don't notice it. To that end, I hit the red line without problems after getting through the 2,000-4,500 RPM range.

Sometimes at idle - and accelerating through the 2,000-4,500 RPM range the car will momentarily stumble as if it looses power. It then snaps back to idle speed or accelerates if that is what I'm doing. It usually does this stumble twice in the accelerating process. That said the car always starts, never stalls or fails to (ultimately) accelerate. But it always stumbles.

I ran codes.
With KOEO - I got 41, 42 and a 65. The 65 is not listed in the code chart???

With KOER - I got a 25 (but didn't strike the manifolds, so that is likely why) and a 74. The 74 is not listed in the code chart.

I have just replaced the head and it has a new valve job. Please note this problem existed before the head change. It was just that the previously burnt exhaust valve was hindering me to properly detect this problem. All the cylinders are now around 150 PSI.

So far I have replaced the fuel filter, air filter, spark plugs, the TFI, and the fuel regulator. I have inspected all the hoses and wiring. I've slide the connectors on/off for a clean contact. I correctly set the timing with the spout removed. The plug wires look good and check out fine with an Ohm meter. Note too that even though an hour had gone by there was a lot of pressure present when I pulled the fuel regulator. So, I don't think the injectors are leaking.

While running I have disconnected the fuel regulator, the EGR, the O2 sensor and the sensor cluster (Knock, Temp etc.). NONE of these has made a change in the miss at idle or the stumble during the 2,000-4,500 RPM acceleration.

I opened the VAM to check the wear on the wiper section. While it showed no signs of wear through on the resistive pad, I did reposition the wiper slightly downward to wear in the same, but new pattern. This changed no aspects of the problem and added no new ones.

I'm incline to rule out the fuel system because the car will go to the redline (on the road) after it gets through the 2,000-4,500 RPM stumble. For that matter doesn't the ignition get worst in the higher RPM range? So, I'm left to wonder???

Any information would be appreciated.

Thank you, Tom
'88, 5 Speed, LA-3, Basically stock (EGR removed)
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zip Offline
Member
#2
Did you check the tps? When does it happen, while accelerating normally and/or while boosting?
Matt
86 TC 5spd:QH/SD,Walbro190,CFI 52#, AFPR,WB,FMIC,3"dp to axle, .63 T3, E6,Stock Longblock.
Shelf:N/A 2.3, Die grinder, Carbide Burrs.
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Wittsend Offline
Junior Member
#3
Zip,
No test on the TPS, but the TPS did not show up as a code so I assumed it was OK. I'll ohm it out tomorrow and see.

On or off boost doesn't seem to matter. It is just the 2,000-4,500 range issue. If I'm off boost it misses quite a bit. If I'm on boost it does the double stumble thing I mentioned. But, on boost it passes through the 2,000-4,500 RPM range quicker.

Thanks, Tom
'88, 5 Speed, LA-3, Basically stock (EGR removed)
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thumper Offline
Posting Freak
#4
Sounds a bit like problems I'm having, except its not regular enough to imply thedouble stumble and is lower in the RPM range (1000-2500).

With that said i haven't found the source of my troubles yet. I have some current leads, but like everything else i fixed (which is everything) I doubt they will solve it.

Not to poop on your parade, but I hope you have better luck than I have so far. You might check out my thread "CAN'T SOLVE THIS MISS! STILL NOT FIXED!" in this same section of the forums...
A.K.A. Corey Bennett

1988 TC: white, all options, 5-speed swap, K&N cone filter, "Ranger" roller camshaft, .60/.63 T3, NXS (Gillis-style) Boost Valve, Bosch BOV w/ check valve, Stinger 3" with axle dump (18" glass pack), 95A 3G

Some pictures: http://s639.photobucket.com/albums/uu111/cbennett4041/
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thesvtman Offline
Junior Member
#5
This must be a common problem cause i'm in the same range as thumper. a little frustrating cause none of the threads show a completion of the problem! Some one HELP US!
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Wittsend Offline
Junior Member
#6
Thumper, Thesvtman,

Thumper I followed your post in hope of.... .

My Bird ran fine for many years. Unfortunately the radiator blew apart one too many times and eventually cooked the gasket. I got another head and prepared it to go before making the swap.

As best I could tell head #2 had an exhaust seat deformity. The valve probably conformed to the seat, but I lapped the valves to clean them up. This likely had the deformity of the seat and the valve misaligned on assembly. Not many miles after it started to run crappy and I parked the car.

I parked the car for about four years (failed smog) and then put the whole engine trans package (including the wire harness) In a '73 Pinto. The swap had nothing to do with my issues as they were all there in the Bird.


With everything I've tried I'm going to assume the O2 sensor next. I also noticed that I don't have a ground wire going to the turbo inlet. I assume it is the orange wire off the line that runs to the BPS. So, that is my next approach. Hopefully we will all get it sorted out.
Tom
'88, 5 Speed, LA-3, Basically stock (EGR removed)
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Pete D Offline
Administrator
#7
Tom,

1. You need to get that orange wire hooked up to the compressor inlet. I don't know how you got the codes without it hooked up. It's suppose to be necessary.

Code 74 is you didn't step on the brake pedal at the right time - don't worry about it.

Code 65 is engine didn't go into closed loop mode. This is a result of the codes 41 & 42 so you need to find what's causing those. In the case of multiple CM codes, I would suggest you erase them. Drive the car a little and then see what comes back

The importance of Tune up parts can't be overstated, especially for this kind of problem. Having a fresh tuneup with the correct parts id paramount. Plug wires are especially critical and just because the ohm out doesn't mean they are good. There are only a few brands that don't cause problems. Two of those are the WR-4011-C is the Motorcraft #. Magnacores are also reported to work well. For plugs, tow that work are Autolite 764 copper or Motorcraft AWSF32-C or NKG # 2238.
The NKG # may have changed.

Did you ever run a compression or leak down test in relation to the valve/seat deformity issue.?
Every get a vacuum reading at warm idle?

thesvtman - unfortunately there are some people here that ask a lot of questions and want time & answers from others but when they solve their problem they won't take the time to update their posts with the solutions for the benefit of others.
Pete Dunham


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thumper Offline
Posting Freak
#8
I hear ya on not reporting back on the solution! I'm dead set on keeping up on old post.... assuming I ever fix the bird.

I have some NAPA wires... I've got some Motorcraft coming. Hopefully they work. I'll let you know. Wink

My other lead: my crankcase breather on the VC is super loose. I'm going to put a new grommet in and see if I can't get a better seal. Hypothesis: loose grommet equals possible unmetered air entering through PCV valve at high vacuum (i.e. at idle, while revving, and under low load). I'm hopeful, but not optimistic.

Its comforting to know others have this problem, I guess? I didn't find any info while searching fo this type of problem. At least maybe we'll be there for others in the future??? Big Grin
A.K.A. Corey Bennett

1988 TC: white, all options, 5-speed swap, K&N cone filter, "Ranger" roller camshaft, .60/.63 T3, NXS (Gillis-style) Boost Valve, Bosch BOV w/ check valve, Stinger 3" with axle dump (18" glass pack), 95A 3G

Some pictures: http://s639.photobucket.com/albums/uu111/cbennett4041/
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xcrunnerbd Offline
Posting Freak
#9
Everyone has had idle or missing issues with their car at one time or another. Most of the time a tuneup will fix it. Other times its adjusting TPS, cleaning IAC. Sometimes though, you need to get nitty gritty. I have had 2 miss issues that I needed to get nitty gritty with. First was a bit easy - fell on its face/bogged under WOT at and above 3k. Fixed with fuel pump.

The other was a poor, barely running cold idle. It ran fine when warm. Fixed with a new ECT Sensor. This sensor did not set a sensor specific code, it did set a code 42 (rich). I used the info here to test it, which it failed (cold temp#'s were off, warm #'s were good - codes run on warm engine) :

http://fordfuelinjection.com/index.php?p=28

So, what I would do is - you have 41,42 codes and haven't adjusted the TPS. Start there. Instructions are in both - TC FAQ and Tech. Articles at the top of the page. Something is triggering your 41,42's - a few sensors will rarely set codes but you can test them. They just may not be "bad enough" to set a code.

As Pete mentioned, not many post back with a follow up: I did this and it worked post. What I did when looking my problems up and saw that was look at the suggestions. USUALLY, but not always the solution was one of the last things suggested. Especially in a longer thread.
Project 13 sec. / 30mpg in '88 TC 5Speed : 15.91@89mph / 32+ mpg

On The Car: KN cone, 2-stage Gillis@ 15psi wired to fuel switch, Kirban AFPR @ 39psi, Walbro 255 HP FP, 130A 3G Alt., Full 3" Stinger Exhaust incl. cat. no muffler,

Shelf: .48 T3, ported E6, BPV
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Matt S Offline
Posting Freak
#10
I highly suggest making sure all the sensors are new and of high quality (not oreilly's/autozone/csk parts store), as well as all the other stuff you know.

I ran around once without the orange wire grounded (forgot when the turbo went in) and it ran just like you describe in the 2k-4k range unless it was under boost. The computer relies on the o2 sensor for fuel mixture until about half throttle. At least that's when my narrow band sensor shows it stop switching.

The stumble - almost die - at idle is a feature of alot of our cars if you didn't know.

Replacing/upgrading parts all had minor improvements incrementally as they were done. Not having done all of that at one time I think I couldn't tell the minor improvements and I didn't really think they did much at all. But my wife hadn't been driving with me for almost a year while I battled what I thought to be a PITA since the day I bought the car. For a while I blamed it on the torque converter until the 5 speed went in. When she did finally ride in it after all the improvements she said she thought it was much smoother than it was before.

I'm still not 100% happy, but I think she's right. I still get some idle issues 20% of the time; seems to be more so when it's hot outside. And I do have some breakup/miss between 2500 and 4500 rpms under heavy load. I attribute that to having boost set at 21lbs and so I'm on the ragged edge of injector capability. I do leave my ks connected but I haven't bothered to turn down the gillis since it's just way too much fun either way Big Grin .

Yeah I fell everone's pain too. BTDT.
Sold it Sad*
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