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Topic: Troubleshooting persistent misfire (Read 2160 times) previous topic - next topic

Re: Troubleshooting persistent misfire

Reply #30
Off topic, but it will be nice to have these seats in there soon, without a broken driver side seat back (passenger side bottom with driver side top sitting here protected):




Various projects are still underway!
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #31
I am curious about the distributor/tif/pip too. 
Just for S&G's run a temporary extra ground cable to the coil and if that makes no different maybe move it to the EEC and check.
I don't know how these ECM's and coils work.  Is the coil hot the entire time and only controlled by the distributor or is the voltage increased by the computer for the load parameter?
1988 Thunderbird TC, 5spd
Stinger single exhaust, Cone Filter, Adjustable Cam Pulley, Ranger roller cam conversion,
'93 Mustang Cobra replica wheels on 235/50R17

'16 F150 XLT 5.0
'17 Husqvarna TX300

Re: Troubleshooting persistent misfire

Reply #32
I can do that one of these days - one long 8awg wire hooked to the battery and attached to a test point on the other end would be quick to do, and be a perfectly fine size to test anywhere on the vehicle.
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #33
Quarterhorse replacement is due for delivery this Friday, so I will be able to test behavior changes via tune post-coil-change this weekend.
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #34
So you are sourcing another ignition coil for testing?

I assume your first test will be stock 19lb injectors and a stock MAF, then go from there.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Re: Troubleshooting persistent misfire

Reply #35
Per #28, I installed a new coil and it fixed much of my degrading ignition issue, but I'm back now to trying to identify the original problem I've been experiencing for the last decade - smoothing out the idle.

My one problem turned into 2 problems. New coil, I'm back to one problem now.
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #36
Per #28, I installed a new coil and it fixed much of my degrading ignition issue, but I'm back now to trying to identify the original problem I've been experiencing for the last decade - smoothing out the idle.

My one problem turned into 2 problems. New coil, I'm back to one problem now.

Jebus I missed the new coil part.


I'm surprised that the idle isn't smoother with the stock cam. I have a Comp 266 HR cam in mine and the idle stays steady in a 50-60 rpm window when it's hot. It's set for 650RPM hot in gear and stays between 650-700 rpm (on an Autometer tach).
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Re: Troubleshooting persistent misfire

Reply #37
Sadly no Quarterhorse today - it will be Monday I'm sure. The plane transport to my city was delayed/late last night, and the tracking still doesn't show it being on a truck for delivery. It's in town, but tracking shows it being in the distribution center since 8:15AM.

This means that I won't be able to get datalogs for a full additional week, the following weekend.

Actually, it looks like they shipped this to my house instead of requested office address. I may be receiving it tomorrow.
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #38
Keep us posted. At this point I want to know what it is just to satisfy my curiosity.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Re: Troubleshooting persistent misfire

Reply #39
Imagine being haunted by it for some 10+ years! It has always ran fine (was daily driving back then), but I can only "just drive it" for so long. Especially now that it's my "toy" car, I want it to run correctly!

I purchased my Quarterhorse in 2010 thinking a tune would help (had a TwEECer before it). No matter what I tried, the tweaking of values in an attempt to improve metering and ignition quality didn't smooth anything out.

Of course I had other driveability issues with my previous 4r70w, which stole my time for awhile. VB, clutches, pressures all looked and tested great for a 13k mile tranny. Had it apart for an output shaft change. This was another issue that I wanted to identify the root cause of, but in the end I completely replaced the transmission and that issue was resolved. Then the car sat untouched for a few years, and here we are today. Idle quality issue persists. I've suspected that it may be related to a part of the harness/electrical, but so far I haven't found an actual problem with it.
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #40
When was the last time you replaced your spark plugs and what gap are they currently at? Have you always used those autolites and are they the stock heat range? They appear to be but just checking. Just grasping at straws for now, hopefully something in the datalog pops out next week.

Re: Troubleshooting persistent misfire

Reply #41
When was the last time you replaced your spark plugs and what gap are they currently at? Have you always used those autolites and are they the stock heat range? They appear to be but just checking. Just grasping at straws for now, hopefully something in the datalog pops out next week.

They have like 100 miles on them.  Maybe 200? Add a few hours of idling, and moving the car around the property. Heads were installed in old house. I drove it on the highway a bit for tuning. Drove it once for gear swap. Drove it from old house to new house. Drove it for transmission swap. Drove it for new front and rear glass. Not much other than that since the topend was changed years back, in which I hoped would improve the motor smoothness. It didn't.

Much of the engine bay as it sits now have nearly no mileage, and the block being the oldest was rebuilt at 228k miles (248k on the odometer now).  The tw170 heads have almost no miles per the above, along with the plugs and wires, waterpump, alternator, power steering pump, battery, throttle body, iac, egr, pcv, and tps sensor. Shortblock had gt40p heads before these, with about 20k miles I put on them as a daily driver. When I had the heads off for head swap, the cylinders still looked new, and was also when I clay'd the ptv clearance, and did some crude injector flow testing to see if any injector was having a problem. Never consumed oil (beyond what pcv fumes suck up into the runners) when I ran the gt40p heads, but I have almost no real mileage experience with the tw170, being that the car sits and all. My legacy troubleshooting started before the new topend parts though.

I don't believe I've had any other plugs on these heads - just these 3924 that were stocked at the parts store and correct for the head, but my idle concern still went back to those iron heads iirc. Years ago I tackled this issue thinking that perhaps my FMS plug wires were bad, so I picked up both these MSD, and other Firecore50's that I haven't even installed yet (those things don't come with the coil wire crimped).

The plugs were at 0.042, but I opened them up to 0.050 when I swapped the injectors to 19lb a couple weeks back. Didn't seem to change anything, but that may be what made my 4k breakup appear with the old coil. I hadn't seen that breakup previously on this coil - just on an Accel coil I tried a few years ago (above 2.5k rpm).

This persistent issue has killed my interest for too many years, and it must end soon! Spending a lot of time and money on the car now, completing other projects that I've been building up in my mind for almost 20 years.
1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #42
Quarterhose did come this afternoon. Will get the car moved over and access into the passenger footwell (and replace passenger seat) tomorrow. Some contact cleaner and I should be good to throw this on again.

1988 Thunderbird Sport

Re: Troubleshooting persistent misfire

Reply #43
That looks pretty, so reading back through this post looks like you have swapped out a lot of things, as of right now what maf and injectors are on the car and around what afr are you shooting for? You also mentioned youve only changed CID what is your SARCHG at? Im trying to figure out if something is going on in your maf transfer or load scaling. Maybe once you get your computer going you can send me the .bin file. Ive had idle issues in the past ive been able to tune out with idle adjustments but thats not ideal. I feel like you probably want to get to the bottom of it. A good start may be a base idle relearn if you havent already

http://efidynotuning.com/idleair.htm


Re: Troubleshooting persistent misfire

Reply #44
That looks pretty, so reading back through this post looks like you have swapped out a lot of things, as of right now what maf and injectors are on the car and around what afr are you shooting for? You also mentioned youve only changed CID what is your SARCHG at? Im trying to figure out if something is going on in your maf transfer or load scaling. Maybe once you get your computer going you can send me the .bin file. Ive had idle issues in the past ive been able to tune out with idle adjustments but thats not ideal. I feel like you probably want to get to the bottom of it. A good start may be a base idle relearn if you havent already

http://efidynotuning.com/idleair.htm



I have the stock '89 Mustang MAF and EV1 19lb pintle injectors that I rebuilt. Prior to a couple weeks ago I had my PMAS 75mm MAF and 30lb injectors, each with their values input. I was hoping to see it run better going back to parts that the computer was configured for out of the box, but no go. I will leave the stock parts on there until this gets solved, if at all.

In the past I've also used 19lb EV6 injectors and 24lb EV6 injectors (the size that the MAF is "calibrated" for).
1988 Thunderbird Sport