88 Ford Van

Hello to all , this is my first time, of course I am having problems with my 88 ford half ton custom van with a 5.0 engine. Problems being the key word, I'm not sure if it is one thing causing the problem.  I've had the van for about a year and a half ,  so I kind of like it.  Being old but not badly maintained it is still a decent ride, in other words I expect it needs money thrown at it, just where and how much is the question. 
 My worst problem is that it is not idling properly . This just started recently , It was running hot on the temp gauge and leaking water so I replaced the thermostat (Quite the pain till I learned the trick) and replaced most of the leaking hoses. I dont think this caused the problem, I also replaced the rotor and cap , the cap was pretty wasted, and fairly old like the spark plugs , I'd replaced a few months back. 
 I'm not sure if my problem is electrical or vacuum , it does have duel gas tanks and a bunch of things to go wrong there. On the highway it seems to run ok but at a stop it starts idling erratically and then dies. It starts right back up, but I smell like a bad gas smell. My check engine light comes on if I'm driving slow but goes off at about 30 .    Another clue is that it idles worse, higher when I run the heater. It almost runs ok with the heater off, perfect for winter driving.    
 I'm basically looking for things to try next. Or first would be best. I've thought of getting the things that could be causing the problem at a junk yard and replacing them until I notice a difference.    I know of the IAC and the ERG maybe , also read of a temp sensor on the throttle body?   It needs some other things like a power brake booster that leaks air.   I'm not very technical but willing to do the homework. Any thoughts will help and thanks for letting me post here.

One trick to try if it’s the IAC valve causing the idle problem on a Ford is, while the engine is idling at temperature, take the handle of a screwdriver and rap on the IAC valve. If the engine idle speed changes the IAC valve is bad.


thank you I will try that.

Most auto parts stores will read the codes for you for free. They will be in a PXXX format and post those code numbers here for us. Then we may have a little more info to give you a better answer.


Yosemite, it’s an '88, so it’s OBD-I. The test connector needs to be jumped and codes read by reading the blinks on the CEL. I’m wondering if the fuel injectors are dirty. Reading the spark plugs can tell you if an injector or two are acting up.

“It needs some other things like a power brake booster that leaks air.”

Fix that first. It may solve the idle problem.

If your power brake booster is leaking air as you said it creates a vacuum leak and will cause a low idle, but less pronounced at higher speeds. Has anyone messed with the throttle body idle adjustment screw ? This is used to set the base idle with the IAC disconnected and should not be messed with after setting it up. Also an EGR valve not closing all the way can cause your symptoms. You need to pull the codes just using a paper clip. You have to place this between connecting points on 2 female connectors located near the driver side firewall…These maybe located elsewhere as I am going by my 89 5.0 in my stang. You can also check the TPS by using a simple voltmeter.

thanks for the help, I will over the weekend be getting busy on it. I was afraid that it is too old for the auto parts code readers . I was thinking on getting a VOM meter to read the blinks testing the iac (I like the idea of tapping on it, though my dad suggested using a really big hammer) and replacing the brake booster.
Is there a good way to clean out the fuel injectors without getting into the throttle body? I normally have dumped fuel injector cleaner in the gas usually about once every couple of months , but it is due .
I’d also like to work on the heater besides effecting the idle it has been stuck on default , where this one blows heat out everywhere. Not the defog.
Thanks again for the help and I will keep posting the results .

A Seafoam treatment is commonly recommended here for fuel system cleaning. Search this message board for “Seafoam” for more details.

I also agree with fixing the vacuum leak first.

1988 is when they were converting from carburetors to fuel injection…The emissions systems used back then can be a nightmare with the technology changing every 6 months…

Here is the procedure for reading the codes.




My initial thoughts when I started reading your post was the O2 sensor, but they don’t always turn on the CEL. There usually is a separate port that you plug a voltmeter into to test this, you will need to google for the test, or join one of the forums I have linked to and see if that question has been asked there before.

Thanks all I will read up on the codes link, But it’s breaking my heart, today I drove to work , it was running pretty good , stopped at a store , when I came back out it wouldn’t start. It cranks but wouldn’t run. So I had it towed, two hours later at home I tried it and it started ran ok , then when it got warm I shut it back off and it wouldn’t start again. Let it cool off for an hour or more and it started turned it off and now it wont run at all. I tried changing the fuel pressure valve and it hasn’t run since. By spraying starter fluid into the throttle body it will run, but not by itself.
I’m out of ideas but I’m kind of stuck with it.

have you cleaned the aic valve yet?

no I did check it (tapped on it with a screwdriver while it was running at warm idle )it didn’tr seem to have an effect

My 70’s Ford truck sometimes gets this symptom, all of a sudden like. Fine one day, won’t idle well the next. Every time it has been some kind of vacuum problem or another. Hose came disconnected, hose split, hose cracked at the connector, vacuum operated device has a leaky diaphragm. I use one of those inexpensive hand-held vacuum pumps with gauge and check the whole vacuum system from beginning to end as the first order of business when I have this problem.

Runs good cold but not hot, often that points to the ECTS engine coolant temperature sensor. Best to get the codes first though.

You’re right @Bustedknuckles, I should have paid closer attention to her…the cars age.

I’d concentrate on getting a new booster and eliminating that as the source of the vacuum leak.
You need one anyway!!!


I looked for vacuum leaks today( tried the spray the hoses and connectors with carburetor cleaner) I guess good news was no fire anyway. Since I now have to get it running to get back to my problems , tomorrow I will try and test the fuel pump. I was told to disconnect a fuel line past the fuel regulator to see if gas comes out to see if I’m pumping enough gas to make it loop into the tank.
My uncle a mechanic said if the fuel pump wasn’t putting enough pressure to the system , when the engine got hot and was turned off the gas vaporizes and the fuel pump isn’t strong enough to push the gas past the vapor.
A fuel pump has got to be real fun on a duel tank. Does anyone know if I have to pull both tanks to get to the pump? Also should I plan on replacing the smaller pumps in the tank?
If I can get it running I think attacking the vacuum leaks with a tester is a good idea.
I also have to start wondering at which point I have to give up on it.

This should be a TFI model and ignition modules are prone to failure on all Fords equipped with them.

I did not pull a schematic for this van but if you look by the diagnostic link connector you should see an individual wire which is tan with a green stripe. That connector is a splice into the ground through the ECM for the trigger circuit of the fuel pump relay.

Run a jumper wire from that connector and ground it on the body or engine, etc. You should hear the fuel pump run and the engine should start and run assuming it’s not a lack of spark issue.
This is for test purposes only; do not leave the jumper in place.

If the van runs with the jumper then you there is possibly a faulty ignition module, ignition switch, or failed ground circuit in the ECM. You might post back with the results of a jumper wire and we can wild guess this some more… :smile:

I’d like to add to my last reply , I’m not really good at quiting on a ride. My last van an 89 doge I had for 9 years. I used to joke I was going to drive it until the tires fell off, then I was going to put the tires back on and drive it some more.
Which I thought was funny until a tire actually fell off, (totally my fault) and I had to actually put another tire on it and drove on. The tire that fell off broke when it hit a bridge pillar. About a year later it just got to be too much wrong with it, so I switched to this one. I have always needed a van for work , mostly carpet, I like the custom vans over the cargo vans, I mean power windows and locks alone, but swivel reclining bucket seats are a big plus to me.
Reason I say this is I could buy a 2004 cargo van for a grand that needs a water pump. It’s also a 360 engine and 3 quarter ton which means constant trips to the gas station. Still I dont know . Give up on one broken ride for the next broken ride?