ok so i checked tps voltage and t was in range. then i disconnected the MAF and it went from idling at 1000RPM to about 850 but would jump around a bit trying to find a good place to idle. i dont think its the MAF because that was replaced no more then a year ago. then i went ahead and took a look at the fuel lines going into the rail and i untightened them nd measured the diameter of their ends and they are veatly different. I didnt actually switch them because thqt would entail removing the ac bracket. But there is no way they can be switched. at least not with the stock hard lines. Anymore suggestions? Should i buy that program you mentioned to see where the sensor readings are at? Thanks again
DAN

 

It would be easier to spot the cause of the problem if you had a data logger that shows the actual numbers the sensors are generating. It pays for itself in short order and you'll find yourself using it again and again over the years.

I've been trying to help a couple of other Forum members with their problems and it's EXTREMELY difficult to track down the cause without knowing the numbers. I, and others, have spent days posting 'check this and check that'. We all want to help, but it's SOOOOOOOO much easier to know the sensor output numbers.

Did you do the IAC manual reset, the one that I posted about?

Is your system going closed loop? Did you check for that?

Vacuum gauge to check for a vacuum leak?

Did you try attaching your timing light to #1 and checking to see that the ECM is taking over the timing chores? If it is, timing should be in the low 20s BTDC with the engine idling. If not check that the EST wire is connected (tan with black stripe near brake booster).

In fact, attach it to each wire to check that voltage is passing through each wire; you should see a steady, uninterrupted blinking.

Some of this I may have suggested before, if so, sorry, can't keep track since I've made the same recommendations many times recently.

Keep us posted.

Jake

 

Your original post says you just rebuilt the engine. What mods did you make?

Lifter preload? One lifter could be too tight; this usually causes a bad idle rather than the engine shutting off completely. Any back-firing?

A vacuum leak is quite likely too and most often is the intake manifold to head, or runners.

Another point I know about on the 86 (so I'm assuming it applies to the 87) is that the lower runner to intake manifold gaskets are side specific. If two of them are installed on the wrong side (switched), you'll get a big time vacuum leak.

I don't want to recommend tearing into the engine to check for that just yet. First check the easiest things.

Use a un-lit propane bottle (Ace hardware) or just plain water to flood the intake gasket areas, if the engine stumbles, you've found your leak. Don't be stingy with the water either.

Leaks occur where the injectors enter the intake manifold too.

I've had my share of vacuum leaks over the years, so I know the problems they can cause. The locations I listed are the most common ones.

It's probably something simple, just a matter of finding it.

Jake

 

What was the TPS voltage reading you took with a digital volt meter?

Did you set the base timing with the EST disconnected? Clear the code when you finished?

Coolant temp sensor in the intake manifold (not the one in the head) is used by the ECM for it's calculations. Is it connected, clean, working? It can cause all sorts of running problems too.

I'd like to see the numbers, remember it's ALL about the numbers:

Lifter preload, base ignition timing, TPS, IAC counts, 02 voltage readings and cross-counts, minimum airflow RPM setting, idle RPM, cam specs, fuel pressure, and any others you can come up with.

I didn't think it was possible to mis-connect the fuel lines but one member posted that's what he did. He installed the pressure on the return and the return on the pressure.

Just some more stuff I've thought of.

Jake

 

Thanks I'll check these things and get back to you