Ok, so i put a new engine into my van(1993 4WD, 4.0L). It has always idles rough since i baught it about 6 months ago, but now the trans went, and the morons at the shop are trying to tell me they cant set up the trans because it idles rough. Anyway, the check engine light keeps coming on, so i checked the code and it said it was the throttle body temp sensor. I replaced that, it ran smooth for about an hour, then it went back to its old self. Well, now the check engine light is back on, but when i chekc for codes, i get nothing. Tomorrow i am replacing the engine temp sensor(for some reason the temp gauge works sometimes, sometimes doesnt since the old engine exploded).

has anyone had anything like this happen to their van? any ideas on the problem?

 

When you say that "checking the codes you get nothing", do you mean that you get a code 111 or do you mean that you cannot get any reading from your scanner? It makes a big difference.

The engine coolant temperature sensor on my 92 3.0L is a different sensor than the sensor used for the temperature gauge. As I understand it, though, from checking my Chilton's, the 4.0L engines may use the same sensor for both the engine coolant temperature signal sent to the EEC (PCM) computer and the temperature gauge. Since your temperature gauge is not working correctly, changing this sensor might be necessary.

On the rough idle, I'd check the IAC valve and all vacuum lines before going any further with changing parts.

Just my 2cents.

Ron

 

I cant get any codes at all. i checked all the vaccume lines, and they are all good, ill check the IAC valve. i didnt even think about that. somtimes it surges at well.

 

A check engine light without being able to get any response from the code reader usually indicates that the EEC (PCM) computer has entered into HLOS (hardware limited mode) and rather than running off the actual signals from the sensors, the engine is running on preset values included in the EEC software. This is caused when a sufficient number of sensors are so far out of range that the computer determines it cannot use their inputs. I'm not sure which sensors cause the computer to go into HLOS mode, but it causes the engine to run/idle very rough. You either have multiple sensor problems, or...

Recently my 92 3.0L would periodically go into HLOS mode causing hard to no start and, when started, very rough running. While in HLOS mode, the check engine light is on, the fuel pump runs constantly with the key in the "Run" position (KOEO). When the problem would dissappear, the code reader would return codes 111, 10, 111 in test mode KOEO and KOER, thereby providing no help. After changing the O2 sensor, the ECT sensor, throttle position sensor, IAT sensor, plugs, wires, distributor cap, rotor, fuel pressure regulator, oil and oil filter, I finally began troubleshooting the wiring. I found that while the CE light was on with the fuel pump running constantly, the WOT (wide open throttle) relay seemed to be cycling on and off on its own whether or not the a/c was on or off. In addition, the Brake and ABS lights were coming on and off periodically. Ultimately I traced things down to a probable power short somewhere between the firewall connector (located just below the EEC connector on the driver's side firewall) and the relay group. When I removed the dust covers from both the EEC connector and the firewall electrical connector and began moving the wires to try and locate the short, the problem went away. So I know I have a periodic short somewhere, but until it happens again I can't locate it.

Check these wiring harnesses and connectors.

Just a thought.

Ron

 

that is ecaxtly what is happening to mine(minus the hard starting). the "Rear ABS" light started coming on lately. How would i go about getting it out of HLOS mode? i have replaced all the sensors other than the TPS but it is still running like poo
Tomorrow i will spend the day checking the wiring. This ought to be fun...Rigggggght. i really like to do my own work, but it seems that my this problem is a bit above my mechanical knowledge, so i may just take it into a different shop. Man, this thing is a money pit. im into it for $5300 CDN already.

 

There is a grey square plastic plug on the big harness near the battery on the firewall. Check and make sure it's plugged in. Someone on the forum had a bad time with his van until he found out that the plug was missing. That plug, once removed, will disable some or maybe all computer engine management functions.

Also, who put in the engine for you? Was it a short block or a long block? Unfortunately, there are several versions of the 4.0L for the Aerostar. A specific head must go with a specific engine block, and that combination must match the calibration curve for the engine computer you have.

Sorry if I alarmed you. That's not the intention. I just want to bring up a remote possibility.

Regards

 

it was just a local mechanic shop. i know the guy who owns it, so i get a good price. it was a complete long block. how would i check to see if it is the right engine? is there a code somewhere on the block?

 

I'm trying to get the sequence of events clear in my head. Exactly why did you have to replace the engine? After the engine was changed, did the engine ever run correctly before starting this problem? What was wrong with the transmission that you felt it needed to be changed? When in the sequence did this transmission problem first show up?

First I would check every sensor on the engine to be sure that it has been connected to the engine harness correctly (i.e. to the correct engine harness connector). Then, disconnect the battery for at least ten minutes to clear the computer memory so it can "learn" the new sensors. Remember, it will probably run bad for a little while until the computer adjusts to the different sensor values. Then check all the vacuum hoses for leaks and all vacuum connections on the engine to be sure they are used or capped off. Next, check both the electrical connector to the EEC (PCM) computer and the firewall electrical connector for bent or shorted pins.

If all this fails to resolve the HLOS problem, then I'd begin checking each sensor as per the repair manual to be sure it operates correctly. (You might do a google search for "gtest.pdf" and scan through this file. You'll need to have Acrobat Reader to view the file)

Ron