Another Respected Tech Tosses In The Towel!

[demarpaint]

I've been working on a problem I have with my E-150 for quite some time now, and just had another mechanic toss in the towel after a week of head scratching. I have an engine surge problem when the engine is restarted hot, it will search for an idle speed until the gas pedal is touched, then stabilize. It starts fine cold although seems to lack a little power until it starts to warm up. Sometimes taking off it will stumble, then race up, as the computer compensates. It is a stick shift, and it is not driver error, confirmed by several others driving it. At times when the AC compressor kicks in it will stumble as well. This doesn't always happen making it more frustriating!

After about 5 mechanics from three different shops went through this van here is what is NOT wrong.

We are 100% certain there are no vacuum leaks, verified now by 3 smoke tests, propane, and carb cleaner testing.

There are no codes

The IAC has been swapped out with others with no improvement, same goes for the TPS.

Throttle body is clean, gasket is new with a Ford updated version.

Gas filter is new, as is cap, rotor, wires, plugs and air filter. Engine timing is spot on. Ignition module is new.

02 Sensor, MAP, CTS, Air Temp Sensor, fuel pump, pressure regulator, are either new or up to spec.

Cat converter is fine, and emission testing is fine.

ECM has been swapped out with another with no improvement.

It responded well to fuel injector cleaning via the rail, but it still has the surge and stumble on occasion when taking off. It was fed MMO via an inverse oiler for many years, so the MMO didn't work its magic on maintaining the injectors.

Here's what I think. The IAC has had a few revisions over the years, the IAC units I've swapped were all FMC parts not knock offs. However I haven't tried an updated version. All mechanics feel it is safe to rule the IAC out. I even installed a spacer plate under the IAC as per a Ford TSB, another waste of time.

All Data has TSB's that report to injectors as being a possible problem, along with the IAC. But once warmed up and moving the van runs flawlessly. The situation is more of a PITA that I want resolved and something I've been told I might just have to live with.

Since this van is not considered a beater I don't mind tinkering, to a point that is. I'm leaning toward injectors, however there is 3.5 hours labor to R&R, and a cost of about $75-$100 each, not something I want to guess at. I won't use rebuilt injectors or injectors that went to a service, because I'm sorry to say I don't want to have problems with them and toss 3.5 hours time out the window. If rebuilt injectors are anything like rebuilt carbs no thanks!

Should I try doubling up on RL FI cleaner for a tank or two, then maybe a mega dose of MMO? Perhaps a third injector cleaning via the rail? Or bite the bullet and live with it, since no one for sure including Ford techs will guarantee replacing injectors will fix this thing?

This should challenge some of the more technical guys here since it has left some of the best area mechanics and myself scratching our heads!

As always thanks!

 

[SrDriver]

I had a similar problem a few years back.

Tried everything and ended up getting rid of the vehicle.

 

[brianl703]

Do a cylinder balance test on it. This could identify a plugged injector.

 

[demarpaint]

Originally Posted By: brianl703
Do a cylinder balance test on it. This could identify a plugged injector.


Something I'll have to look into. Funny thing is these guys say it runs too good to be an injector problem. They were going nuts looking for a vacuum issue, codes or a faulty sensor.

 

[Stu_Rock]

I think it's worth looking at the injectors. I sent a batch of injectors for cleaning and flow metering to a guy in Michigan named Rich Jensen. He did a pretty thorough job and identified a faulty one. It was pretty inexpensive and it really helped out that engine's idle. He didn't even charge me for the faulty injector.

 

[eljefino]

I would get an aftermarket o2 sensor monitor/ af ratio gauge, they are cheap and work with the ECM.

I suspect on a cold start the van runs on open loop until it sees throttle, that blip you give it.

I like the idea of injectors, an unbalance would be most obvious at idle. Maybe this is something an (old) mechanic could diagnose on an ignition scope?

 

[Trav]

Does this use the cone shaped air filter with the big clamp that connect two halves? I have seem more than one of these improperly installed (only half on on the bottom) or rotted out,they will leak behind the MAF and throw no codes.
The MMO inverse oiler will not help with the injector internals as its not going into the fuel system but rather the air intake.

 

[JHZR2]

Bad harness for ICV/TPS? Perhaps a high resistance connection so voltage is present enough to not trip a CEL, but not a good signal for control?

How about a fuel pump issue? Ive had hot start issues due to a weak fuel pump and flaky connection.

 

[punisher]

Ditto on a power balance test to see if it is one or all cylinders causing the problems. Run a relative compression as well if the machine supports it.

Grasping at straws stuff:

Assuming you have AIR injection, verify nothing is blocking the vent nipple on the rear of the air pump. I had a MKVII that drove me to tears with an idle stumble because the air pump was intermittently putting air upstream and throwing off the O2 sensors causing a very temporary rich condition. Happened too fast to catch it with the SBDS.

IAT sensor- wont always set a code, verify the temp is in range.

The only problem prone injectors were on the 300 I6s. More than a few clogged/bad spray patterns.

The AC compressor kicking in causing a stumble is odd. Oh, pull off that spacer plate under the IAC and reset your base idle/idle strategy. Those spacer plates were useless and we fixed our fair share by pulling them off, cleaning the throttle/IAC and resetting everything.

Gotta run.

 

[demarpaint]

Originally Posted By: Trav
Does this use the cone shaped air filter with the big clamp that connect two halves? I have seem more than one of these improperly installed (only half on on the bottom) or rotted out,they will leak behind the MAF and throw no codes.
The MMO inverse oiler will not help with the injector internals as its not going into the fuel system but rather the air intake.


No the filter is a rectangular filter, all plumbing and connections are good. As I mentioned the Inverse oiler doesn't feed MMO through the injectors at all, so they didn't benefit from it. When I pulled the IAC and throttle body both areas were surprisingly clean, so much so that the mechanics even commented.

Would it be worth at this point to try another cleaning via the rail, or a mega dose of Red Line FI Cleaner? That 3.5 hours labor to remove and replace the injectors is quite a job. If the mega cleaning doesn't work then I'd spend the money on an injector balance test. I'll call my guy that had it for the week and ask him if he looked into that. Both him and his partner didn't think it was an injector issue, but there aren't many other options. I was the person suggesting injectors.

 

[demarpaint]

Originally Posted By: punisher
Ditto on a power balance test to see if it is one or all cylinders causing the problems. Run a relative compression as well if the machine supports it.

Grasping at straws stuff:

Assuming you have AIR injection, verify nothing is blocking the vent nipple on the rear of the air pump. I had a MKVII that drove me to tears with an idle stumble because the air pump was intermittently putting air upstream and throwing off the O2 sensors causing a very temporary rich condition. Happened too fast to catch it with the SBDS.

IAT sensor- wont always set a code, verify the temp is in range.

The only problem prone injectors were on the 300 I6s. More than a few clogged/bad spray patterns.

The AC compressor kicking in causing a stumble is odd. Oh, pull off that spacer plate under the IAC and reset your base idle/idle strategy. Those spacer plates were useless and we fixed our fair share by pulling them off, cleaning the throttle/IAC and resetting everything.

Gotta run.



Thanks Punisher, this is a 300 I6, the air pump is working, we checked that early on.

It runs exactly the same with or without the spacer plate. I'm afraid to remove it now because the last guy that had it messed up the stop screw to set the base idle, and I'll have to try and remove that to get a new stop screw in. The base idle is set perfectly with the spacer plate, and I'd rather not mess with it since it made no difference with the plate or without it.

I might be barking up the right tree with these injectors, even though the techs that had it said they didn't feel they were at fault.

Could this be a design issue that effected some of these engines but not all? This is a 1988 and the second year for FI in the 4.9L I6 engine. This issue has annoyed me for years, even Ford couldn't resolve it, now it seems to be a little more annoying since I have a new vehicle to compare it to. LOL

 

[daves66nova]

Can you disconnect 1 injector at a time when it's running rough? If you don't get a idle change,that's the injector.

 

[NYEngineer]

Since you say this only happens when it's cold, did you try swapping the coolant temperature sensor? I had those same symptoms on a vehicle once and that was the problem. No CEL either.

 

[HawkeyeScott]

I'd be curious to hear more about your O2 sensors. Because, you're having some of the same problems/symptoms I was having on my Jeep 4.0 this year. I tried many of the same things you have. IAC, TPS, throttle body, plugs, fuel pressure test, vacuum leaks, etc. I did change one of the 2 upstream O2 sensors after it threw a code. It really didn't help much at all. I didn't get any other codes so I assumed the other upstream O2 sensor was fine. It was not. After running out of other ideas, I researched and found an NGK O2 sensor through O'Reilly's and it fixed my problems. The Jeep is smooth now.

All our problems weren't exactly the same, but they're similar enough you may want to re-examine your 02 upstream sensor(s).

Good luck to you.

 

[shpankey]

Not the same issue as you, but I once had a Trans Am GTA that had some kind of electrical problem. I would burn through alternators about every 3 months. I took it to 2 mechanic shops and 2 old timer mechanic friends (well, father's of friends) and even took it to an electrical shop for cars that does this exact thing. Nobody could ever find the problem. Even replaced the whole wiring harness, ecu, several batteries, alternators and everything under the sun and like clockwork, over a few months it would just start dropping voltage. It was supposed to run between 13.9 to 14.2 but it would just keep dropping. I loved the car. We even custom built the engine and did all kinds of fancy stuff. Crazy quick car with low differential and tranny gearing and I'd put down crazy fast 60ft times at the track. Had 3.5" exhaust, headers and flowmasters and with that built engine it is still the greatest sounding car I've ever had, maybe even ever heard, on take off. Was so painful to let that thing go but I just couldn't waste anymore money trying to fix some mysterious issue that nobody, even pro's couldn't figure out.

I still miss it. lol

Anyhow, my first guess when reading it was injector. Though I'm no mechanic. What about injector seals? I'm just throwing something out there that I have no clue about. haha

 

[mechanicx]

I remember this issue and suggested a injector balance test. You have some good replies here. Since it only acts up when cold, as someone mentioned I would consider looking at the intake air temp sensor and coolant sensor. These sensors can have bad values or have a bad connection and throw the fuel mixture off just enough to cause drivability problems but not set a code.

edit: I reread your post and see that you said the problem happens when hot and you replaced the IAT and TPS, you didn't mention the coolant sensor, but I assume its been checked with a scanner and reads proper operating temp. Let me ask you this. What happens if you unplug the FPR and cap the vacuum hose? This should max out FP and see if that gets rid of the stumble.

 

[demarpaint]

Originally Posted By: daves66nova
Can you disconnect 1 injector at a time when it's running rough? If you don't get a idle change,that's the injector.


That is something I have not tried, but will call the tech that had it last and I will ask him. Sounds easy enough to do though.......thanks


Originally Posted By: NYEngineer
Since you say this only happens when it's cold, did you try swapping the coolant temperature sensor? I had those same symptoms on a vehicle once and that was the problem. No CEL either.


The van starts great cold, since it’s a stick shift it feels a little lacking in power until it starts to warm up. The flip side to the problem is this, lets say its warmed up and I shut her down for 10 minutes or so and restart, it will surge like crazy until I tap the gas pedal. On occasion it will stall on a hot restart, [I forgot to mention that!] Sometimes flipping on the AC will set her into a surge tizzy.

I changed the CTS it didn't do anything. I ran it with the O2 sensor unplugged, it didn't make any difference. Then I got a Ford 02 sensor from a friend and tried it out, he allowed me to return it if it didn't work. Still no luck. It pays to know people in the business .

Originally Posted By: shpankey


Anyhow, my first guess when reading it was injector. Though I'm no mechanic. What about injector seals? I'm just throwing something out there that I have no clue about. haha

I have no electrical issues that I'm aware of. The injector seals are good, confirmed by smoke tests, more than once, and propane tesing.

I'm also going to talk with this tech about a balance test, but as I mentioned him, his boss, and another shop said they doubt it is the injectors. In fact they were extremely confident. I was the one suggesting it, and they certainly aren't going to pass on the work, but won't guarantee the injectors will fix the problem. Which is confusing the [censored] out of me!!!!!!!!!!! It's an expensive gamble, the van is most certainly worth the money to me, but I want to be dammmmmmmmmmm sure before I pony up the cash.

As a side note I did a compression test late spring and the readings were in line with a problem free tight new engine. This beast was babied!

Thanks for all the replys, you guys are great!

 

[mechanicx]

Can you try unplugging the vacuum hose from the fuel pressure regulator and capping the hose? This should raise your fuel pressure some. I think you are getting a lean stumble when hot. Doing this might point to the problem.

 

[demarpaint]

I'll give it a try. What exactly am I looking for? Should I drive it that way? If so for how long?

I did change the FP regulator not long ago, and it didn't improve anything. But that's not to say the part can't be bad, and it is something very easy to try.

Thanks!

 

[Vikas]

What model year? If after 1996, now is the time to cut open your package of the scanner which you have been saving it for a rainy day Seriously, find out what live parameters are supported by the van and notice the difference when it behaves badly vs when it does not.

That is the whole idea of buying a scanner with live data capability. I would concentrate on temperature, throttle position sensor, MAF (or MAP) readings. Any abnormal reading should be investigated.

- Vikas