I have an 88 F150 that was running poorly a few months ago, lack of power and no acceleration. I performed a compression test and it was low around 90 on most cylinders and it was apparent that it had been overheated at one time(This truck is new to me) as there was rusty coolant residue all over the engine compartment. I pulled the motor and re-ringed it and re-installed it. Now that I have it back in, it still lacks power and is backfiring through the air intake which I think it was doing before too. I now have about 140 compression in all holes and performed a leak down test which resulted in less than 10% loss in all cylinders. I pulled the codes and I have a 022 KOEO and a 041 KOER. I have been troubleshooting for two weeks and don't want to write a five page post so please I need help and will answer questions as they are offered. Any suggestions?

 

Code 22: MAP sensor out of self test range.

The computer relies heavily on accurate feedback from the MAP sensor. Check the output with a meter than can measure frequency. If good, verify the wiring back to the computer.

For reference: Manifold Absolute Pressure Sensor (MAP)



Code 41 (KOER): No HEGO switching detected always lean

Could be caused by the faulty MAP, vacuum leaks, exhaust leaks upstream of the O2 sensor, open AIR injection ports.

 

022 - Last night I tested the Map sensor and the Hz readings were within spec. I applied and released vacuum and as per test references the Hz reading slowly increased and decreased with no dead spots. I have a 1990 bronco also so I have extra FORD OEM MAP sensors laying around, I did try swapping them out, no change. I also double checked that I had 5v on my VREF wire, and a good ground for the MAP, checked good. I installed my breakout box and checked my ohms reading on my MAP signal wire, less than 5 ohms so it is in spec. At this it would appear the computer is bad or not recognizing the MAP signal right?



041 - I am 99.9% sure I do not have a vacuum leak, although my VAC gauge readings appear to be low. At idle cold I am around 10 in Hg, after it warms up it climbs to around 14 to 15.5 in Hg. I am at about 2500ft in elevation. I have plugged every vac port on the manifold excpect the MAP port, pinched off the lines going to the canister and made sure the ISC Motor is clean and blocked off the EGR and nothing effects the vacuum. I removed the upper intake plenum and the gasket is good. I feel strongly that the lower intake gasket is good too, however I have no way of being 100%. I didnt think of the Air Injection so I will check that next. What is the best way to test that other than blowing into the hoses? There are 0 exhaust leaks, I made triple sure of that.


Thank you for the response, I appreciate it greatly.

 

As far as the MAP signal goes perhaps there is a bent or pushed pin on the PCM? It's a stretch....I suggest you pull out the PCM, inspect for signs of leaking capacitors. You could also ohm the signal path into the computer for the MAP signal.

Your vacuum readings are low, even for 2500 ft. elevation IMHO. Timing sounds retarded perhaps? Very rare a vacuum leaks causes low vacuum signal...unless it's a HUGE leak. If the AIR injection system was compromised then you typically have exhaust noise/ticking. On the other hand a Check valve could be leaking through without triggering noise.

I would resolve the MAP code and re-check the base timing.

 

I pulled the computer last night and inspected it, I saw nothing out of the ordinary. This particular computer has only one capacitor on the board and it did not appear abnormal. I was able to ohms the signal return wire from the MAP sensor plug to the ECU and it was less than 5 ohms which is within specs. As far as my results are showing my wiring is good, My map sensor is varying in the Hz signal as the Vacuum varies and the reading is in accordance to the specs on the chart of the page you link in your first post. If the sensor is functioning properly and my wiring is not compromised, seems to me it would have to be the computer. Here is a new question for you. I have a 90 Eddie Bauer Bronco also with a 351w automatic although it is an E4OD and the 88 pickup is a C6. As far as I can tell both trucks have the same sensors except the 90 has a Knock and the 88 doesn't. If i install my 90 ECU in my 88 should it run?



I have rechecked the timing 3 or 4 times, SPOUT CONNECTOR unplugged, I am sitting right at 10 degrees......using a Snap-On digital timing light and my advance is set at 0 on the light. I have made sure I'm not a tooth off on the dizzy. I removed the timing cover to make sure I didn't accidentally install the chain wrong, its good. I even pulled the valve covers and rockers and rotated the engine by hand and checked the lobe lift on all the cam lobes to make sure I didn't loose one of the cam lobes, ell measure around .278 intake and .282 exhaust.


I agree with you, I think the MAP code may be causing part or all of the problem with my 041. I am trying to focus on that and give any other info I feel is relative at the same time. Man thanks again for the response, I have been trying to figure this out myself and it is good to have someone to bounce ideas off of and receive ideas from, thank you.

 

Without an E4OD attached the other PCM will trigger a Check Engine Light but it could be used for troubleshooting the MAP code.

 

That was my hope. I installed it and it ran the same if not a little worse. I have attempted to complete the cylinder balance test to see if maybe I lost an injector or two but I can't seem to get the test to complete. Really don't know which way to proceed. I need to think about this some more and hopefully I can get some more ideas coming my way. Thanks RLA! Happy Memorial Day weekend!

 

Speed Density equipped vehicles cannot run the Cylinder Balance test. Only MAF equipped vehicles can.

I wonder if your EGR valve is stuck open. If it were stuck open, then it would create an intake leak and your vacuum reading would be compromised.

I would inspect and also block it off with some thin sheet metal or soda can and see what results you have next. The low vacuum reading will trip the MAP sensor code.

 

Okay thank you for clearing that up about the MAF vrs speed density vehicles and which ones are able to run the test, I didn't know that, thank you.

In my second post I did indicate that I blocked off the EGR when I blocked off everything else to eliminate vacuum leaks. I used two layers of Duct tape and bolted the EGR back on and ran it. When I took the EGR valve back off, the tape had held and was not ripped so I know it is not related to the EGR valve. I actually replaced the EGR valve and exhaust manifold to EGiR valve pipe for the EGR when I did the rebuild as the pipe was broken and the valve housing cracked when I tried to loosen the big nut on the pipe/valve housing. So those things I have covered. But that just brought something to mind that I had forgotten about. On the EGR solenoid there is black box between the solenoid and the solenoid plug, it is the same shape as the plug, almost like a plug extension. I am going of the top of my head but I know that when I tested the solenoid resistance it was in spec but with the black box instsatlled it increased the resistance by 15 or so OHMS. I dont' think it is relevant to the MAP or LEAN code as nothing changed if i removed it, so I left it in but am curious as to what it is. Thanks again Timber.

 

Sorry for not seeing where you had blocked it off. I've read it several times and I have a bad habit of skimming.

I know the solenoid you speak of and that extended piece that is part of it. I have only seen these types on the '87-89 5.8's. Also a few on the old 460's.

That solenoid is commonly referred as the EVR solenoid.

But back to the matter...

Your vacuum is quite low. Have you tried running the engine without the dual intake tubes connected at the throttle body? Dirty air filter or perhaps a restriction in either tube?

Remember, it can be the simplest solution that gets overlooked when doing major repairs.

Is the exhaust new or 27 years old? If so, are the catalytic converters 27 years old? I wonder if exhaust were plugged, as the converters were melted and plugged, would that also cause your backfiring through the intake and subsequent low idle. Air has to go in, but if it can't escape, then it would bog the engine. You did say that it appears the engine overheated badly at some point, the catalytic converters hate coolant and fuel that floods.

Just a few more ideas to help you.

 

Okay s that extended piece is OEM equipment, then I will leave it in the EVR solenoid, thanks for the terminology schooling too.

Ya know I am not sure if I have run it with those disconnected or not. I really can't say for sure so Today I will pull those off after we get back from taking the kids to the Memorial day parade and I will check that.

I knew the converters would surface eventually so here is what I have done so far concerning them. When I was re-installing the motor and moving the exhaust around, I heard a rattle from the rear smaller converter. I have seen many times where a lean running engine melts a portion of the front converter and a chunk ends up in the rear one rattling around. I took the exhaust off and the rear converter was empty and had a piece of exhaust tubing inside making the noise. I took a mirror and did the best I could to inspect the front converter and it looked good, it wasn't melted. I put the exhaust back on and ran it a few times down the road. I then drilled a hole in the pipe in front of the converter and drove it again and it did seems a little better, so I drilled two more and drove it again and I really couldn't tell a difference. Then I welded them all back up and drove it and it seemed the same as with the holes. The vacuum did not change drastically either with or without the holes. I just didn't feel that I gained the increase that I would have had it been a plugged converter. I was also wondering about the effect the holes would have on the O2 sensor as it is right next to where I drilled the holes. I kept thinking I wonder if the ECU is going to pickup a lean reading and richen it up and cause misfires. At that point i was me tally exhausted and it was hard to focus on one thing, I was frustrated. So anyways the exhaust is original, including converters. The truck is supposed to only have about 100,000 miles on it. It is really clean so I think that the miles are correct.

I will update after the intake tube/ air filter inspection I do this morning. Thanks Timber

 

Did you still get a MAP code?

 

When you had the heads removed, what did the machine shop do to them?

 

When I put the other computer from my Bronco in I ran the engine and brought it up to temp turned it off jumped the test connectors and retrieve the codes. This time the codes that I got were 56 67 85 91 92 94 93 and 99, then the separator code came and 3 codes follow that, 56 67 and 99. It still ran poorly and I noticed that by the time it had heated up to temp the little fiberglass sock on the EGR tube was smoking. So I don't know what that was about but apparently the 90 Bronco ECU didn't like being in the 88 F150. So no I didn't get the MAP code but the alternative it produced was much worse.


As far as the heads are concerned I had the heads pressure checked, surfaced and a compete valve job done. I have been wondering if I'm having some valves that are closing when the engine is off(leak down test)and cranking slowly (compression test), but are hanging open when running, just enough to lose a little vacuum and allow the flame front to travel back into the intake.

After thinking about this for a bit, I believe that it was running the same way before the rebuild so I doubt it is the heads. What would the odds be that at 100,000 miles the valves start to stick and then after a complete rebuild on the heads they would be sticking again. Maybe if it had really old gas in it that was gumming the stems up it could be a possibility? Can anyone tell me how far the valve would have to be open before it hit the piston when it comes up to TDC? I feel like I'm reaching now for something or anything. If I'm getting off track someone please set me straight.

 

Can anyone comment on the various codes I received with the 1990 Bronco computer installed? Hoping someone will chime in with some ideas, thanks.