'89 - 302

Just replaced the O2 sensor, the air charge temp sensor, coolant temp sensor, as well as re-installing the spout connector (which has been missing for a while).

Set the timing at 10 degrees BTDC (with spout out) and went for a test drive. It pulls ok over 2K rpm but mis-fires BAD at anything below that. The throttle position seems irrelevant - this is more load or rpm related.

Checked the lines for MAP sensor and everything seems ok there.

Any suggestions? I'm stuck at a guy's house using his computer and need to get home.

 

Was it missing before you did the work ?

 

Ahh, the old if it ain't broke don't fix it route....

About a year ago I tried to re-install the spout connector and got the same problem. So I worked at replacing several of the sensors, plugs etc... and this is first trip on the road with the spout connector back in.

I'm about 99% sure the problem is related to the spout connector, b/c if I take it off the truck will go back to running ok - not great - just ok.

My overall goal is try and get it back so that the computer can control the advance. As is was, the acceleration was a lot like riding on a golf cart - that make any sense?

 

If the PCM cannot control the advance, your Ignition (TFI) module is the most likely culprit. On your 89 its mounted to the distributor. Without the SPOUT connector the timing will NOT CHANGE AT ALL. Removing the SPOUT is like removing the vacuum advance from an old carburated enigine. There is no signal from the computer to advance OR retard the timing as needed. Replace the ignition module and make certain you use plenty of heat sink gel on the backside of it before you put it back onto the dizzy housing. Its a wonder the truck runs above idle AT ALL without the SPOUT installed. The ignition module in conjunction with the PCM control timing. SPOUT connector interrupts the communication between these two. If it doesn't run well once the SPOUT is reinstalled and the TFI module is replaced, pull the codes from the PCM to troubleshoot the additional problems.

 

Yes, that's exactly where our diagnosis left off. We back-probed the SPOUT input at the TFI and found that the voltage (while running) was 5.6v. That is right within the spec of 3-8v. By default, it points to the TFI at this point. But the question still remains (in our heads at least) - even though the TFI is getting a proper signal at idle, we don't have a way to monitor it rolling down the road (read: load).

We also checked the codes and saw one in memory during the KOEO test. It came out as a 32 if I recall correctly which points to an EGR issue. Since this thing is dead smooth at idle and runs 'ok' above 2k, was not a recent code, I am thinking that this is not the root cause, but one that needs to be addressed.

 

Replaced the TFI and it did not get any better.

We set it to 16 BTDC and removed the spout to drive it around and now it's back to running "ok".

With the spout in and set at 10 BTDC it will take off fine, but then spit/sputter at the change from 1st to 2nd when it's between shifts at roughly 1800 or below. If I can get it over 2000 it will lope along but has a very lazy acceleration.

I guess the next thing that I need to understand is Ford's timing strategy. At certain loads, and certain rpms and certain coolant temps, etc. what are the primariy influences in low rpm timing. That is a tough one I know.

Does anyone think that if I were to bring it to a reputable shop and they used their scanner (snap-on, Mac and the like) will that type of tool help pin point the problem? I know grabbing codes is one thing, but this only appears in a ceratin rpm as well as my butt-o-meter is telling me that it happens under more load.

Not a big fan of swapping parts without cause....

 

It almost sounds like the timing at the chain is off by a tooth, just my .02 worth.

 

Hmm.. that may be the case, but I am very confident that the timing chain was replaced at some point in its long history. I have a big stack of receipts, and the guy who previously had it was pretty good about taking care of it (also deducting all expenses as this was his 'work' truck).

We did check for T-chain slop. Did the ratchet on the crank and have someone watch the rotor trick. It was super tight, almost no slop at all (went back and forth several times). This plays into my thoughts that it has been replaced since there is no way a chain can be in 'nearly new' shape at well into the 200k zone.

Any thoughts on the Knock Sensor? Can you unhook it for testing purposes? How much timing can it take out? I am used to the Mustang MAF EEC-IV and the Ford Speed Density with KS is relatively new to me.

I do know that typically the EEC will go back to original look-up tables once the computer is reset or unplugged for a while. Since we replace 3 key sensors it should be on the base table when first started (battery unhooked for over an hour). It can and does learn from there. What gets me is that the bucking was instantly noticeable since there is a hill right in front of my buddy’s house. Also it leads me to believe that there is something not happy as it instantly affected the timing even though I would presume that running right from the base table would be a 'safe' starting point (fuel curves and timing tables).

Sorry.. rambling now... any thoughts out there?

 

Actually code 32 referrs to a malfunction in the EVP (EGR Valve Position ) sensor or its circuit. This either means the EGR is not moving properly OR the EVP is not "reading" the movement of the EGR valve properly. Either will create a compensation reaction in the PCM as it tries to adjust to the apparent malfunction. Timing AND fuel/air ratio adjustments will be made to compensate for the lack of exhaust gasses or "apparent lack" of EG through the combustion cycle.

While you are checking things make absolutely certian that the enitre Thermactor system is functioning. Even if the EGr system is working, if the air injection isn't being properly distributed, you will get all sorts of idle and hesitation problems. I just chased down a bad Thermactor diverter valve and a broken air injection check valve on the crossover tube between the heads. Remedied a multitude of problems with idle and throttle/acceleration response problems.