Tuned car developed misfire

[Reaper]

I rallyX a 16 FIST with a stock engine other than a basic Stratified tune which I've run for a few years. At this weekend's event the engine was gently misfiring at idle and the check engine light came on. While stationary, with the tranny in neutral, or the clutch down, I could not rev past 3000rpm. But when I drove off anyway, all the power and rev range seemed to be there. The CEL came and went out several times throughout the day, but the car competed well. (and won big) Got home and checked the codes. Three codes, all for misfire. Cyl 2, Cyl 3 and Random. I only feel any misfire at slow idle.

Recommendations for troubleshooting? I probably won't be welcome at the Ford dealer with all the racy stuff and tune on the car. I have no idea if the misfire is related to the tune, or something independent.

 

[FiestaSTdude]

I rallyX a 16 FIST with a stock engine other than a basic Stratified tune which I've run for a few years. At this weekend's event the engine was gently misfiring at idle and the check engine light came on. While stationary, with the tranny in neutral, or the clutch down, I could not rev past 3000rpm. But when I drove off anyway, all the power and rev range seemed to be there. The CEL came and went out several times throughout the day, but the car competed well. (and won big) Got home and checked the codes. Three codes, all for misfire. Cyl 2, Cyl 3 and Random. I only feel any misfire at slow idle.

Recommendations for troubleshooting? I probably won't be welcome at the Ford dealer with all the racy stuff and tune on the car. I have no idea if the misfire is related to the tune, or something independent.

No clue about why you have a misfire, but congrats on winning even with it!

 

[ranger024x4]

how old are the spark plugs? have you pulled them? I would check the gap at the very least.

 

[Reaper]

This car is a trailer queen, bought new for racing. Probably has only a couple thousand miles on it...mostly very hard miles.

It bothers me that I'm suddenly getting misfire on at least two cylinders. Seems unlikely that two plugs or two coils would go bad together. Stratified did write back that they think the tune is not involved and to look for mechanical suspects.

Was checking Amazon for replacement coils to use for troubleshooting but they all say for 1.6 Fiesta, don't mention turbo or ST. Are these the right coils or does the ST use a specific part? I may not actually need coils, so I don't want to go overboard on pricing. Anyone have recommendations for decent quality inexpensive coils to try?

 

[kivnul]

Rock auto shows these:


Tasca shows this (oem/motorcraft), which should confirm the rockauto part numbers.


Engine mounts could cause false knock. I would look at all 3 to verify they are all in good shape and secure. My passenger side mount came loose from the subframe and the whole engine was sliding back and forth about 1cm. The main bolt in the middle of the thing is also known to break in half.

Also, loose ground / low voltage can cause some very weird computer issues. Verify the battery is ok and possibly disconnect the ground strap from the firewall, sand the surface to remove paint and rebolt it down. My kids Fiesta had issues before doing this.

 

[SteveS]

Amazon sells that part number BTW

 

[TyphoonFiST]

Buy the NGK* Coils and some Step one colder plugs 6510s from Rock auto.

 

[ranger024x4]

If it were my car, I would take the coils from the 2,3 and swap them with 1, 4 to see if the problem moves. While you are there you could check gap.

 

[Reaper]

Buy the NGK* Coils and some Step one colder plugs 6510s from Rock auto.

Are one-step closer plugs appropriate for a totally stock except tuned motor? Why not 6509s as some have suggested?
The Rock Auto NGK coils are pretty inexpensive, but I've heard of NGK counterfeits. Do we know for sure these are genuine? And as good as OE?

 

[Reaper]

If it were my car, I would take the coils from the 2,3 and swap them with 1, 4 to see if the problem moves. While you are there you could check gap.

I like that approach but the problem was consistent at the event, but intermittent now that it's home. Maybe temperature stress? Dunno. Anyway it makes for difficult part-swapping troubleshooting.

 

[FiestaSTdude]

Are one-step closer plugs appropriate for a totally stock except tuned motor? Why not 6509s as some have suggested?
The Rock Auto NGK coils are pretty inexpensive, but I've heard of NGK counterfeits. Do we know for sure these are genuine? And as good as OE?

There's debate over whether you should use 6509s or 6510s. I actually have a set of both. I'm personally using the 6509s for now, mainly because they are already installed.
I've bought the ngk coils from rock auto and they are fine for me.

 

[Reaper]

Rock Auto order placed. Set of NGK coils and 6509 plugs. Stratified says to gap them to .026". Have seen forum recommendations for .025". Don't expect the difference is significant...I'll call it a range.

 

[Reaper]

I read in another thread that Iridium plugs should not be gapped. I assume not the majority opinion. I suppose the issue is the tiny electrode is subject to damage if you use poor technique. Do people still tap these on a workbench or does everyone use a gapping tool?
https://www.amazon.com/YESHMA-Unive...011&sprefix=spark+plug+,aps,2520&sr=8-37&th=1

 

[gtx3076]

Are one-step closer plugs appropriate for a totally stock except tuned motor? Why not 6509s as some have suggested?
The Rock Auto NGK coils are pretty inexpensive, but I've heard of NGK counterfeits. Do we know for sure these are genuine? And as good as OE?

I've been running stock plugs on full stock+E30 tune for several years now.

I'm just beginning to modify other parts of the car and will switch to step colders if my tuner insists on it.

 

[FiestaSTdude]

I read in another thread that Iridium plugs should not be gapped. I assume not the majority opinion. I suppose the issue is the tiny electrode is subject to damage if you use poor technique. Do people still tap these on a workbench or does everyone use a gapping tool?
https://www.amazon.com/YESHMA-Universal-Caliper-Compatible-Plugs（Red）/dp/B09NLK2BN1/ref=sr_1_37?crid=2RCMJ09QUYLV1&keywords=spark+plug+gapping+tool&qid=1654034998&refinements=p_36:1200-3000&rnid=386419011&sprefix=spark+plug+,aps,2520&sr=8-37&th=1

I gapped my iridium plugs by carefully bending them with pliers and tapping on a metal bench. 25k later they work fine

 

[Jabbit]

I read in another thread that Iridium plugs should not be gapped. I assume not the majority opinion. I suppose the issue is the tiny electrode is subject to damage if you use poor technique. Do people still tap these on a workbench or does everyone use a gapping tool?
https://www.amazon.com/YESHMA-Unive...011&sprefix=spark+plug+,aps,2520&sr=8-37&th=1

I use this, $20 after coupon. Works great.

K-MOTOR PERFORMANCE Spark Plug Gap Tool - 1 Set with Feeler Gauge (14mm Thread) https://www.amazon.com/dp/B07FPVTCQX/ref=cm_sw_r_apan_i_E777BAW03NV070C8JNFM?_encoding=UTF8&psc=1