Issue with hesitation on cold start

[Theodore]

Am looking for some advice. After last weekend’s adventure replacing spark plugs & assorted EFI sensors (IAC, TPS, MAP), + we’ve now got a nice running car, with the exception of acceleration just after a cold start. Have been daily driving the Wagoneer all week, and every day, 3X/day (morning, lunch, & evening) I see the issue, where the car starts, and until the temperature gauge reads above 100 or so, there’s severe hesitation, and often dies pulling out from parking spots and/or red lights/stop signs.

We’re running Affordable Fuel Injection’s EFI setup. Had myself talked into EGR valve issues – that is, til I went out today to discover there’s one there, but there’s no vacuum lines attached, and there’s no EGR/CTO switch to activate it either. This morning, I took it off to check that it could hold vacuum – that’s good; and it was closed – also good, given no vacuum line were connected.

So, I’m wondering whether to attempt to put the EGR/CTO switch & vacuum lines back? Or, do I get a EGR delete plate to block the port? Given parts & lines are missing, I’m wondering what else is missing to get back to scratch.

If it’s not the EGR, what else could cause a severe hesitation at cold start?

[babywag]

best way to diagnose is datalog or scantool to monitor what the sensors are reading/ecm is doing during the problem.

without seeing data any advice is just a guess.

The coolant temp sensors are sometimes bad which results in improper fueling due to incorrect engine temp being reported.
since it is only on cold starts that would be the first suspect.
a datalog or even testing it with an ohm meter will tell you if it is bad.

pretty unusual to need iac/tps/map all @same time, and with shotty quality of aftermarket stuff a big roll of dice.
best to diagnose and replace single sensor @ a time vs. throwing multiple parts.

[Theodore]

Was thinking obd1 didnt provide much of a datalog capability; everything ive seen so far talked about jumping ALDL pins & counting blips of the check engine light. Given the running state of the car, have gotten to the point that i dont trust previous work. The good news is: other than this issue, running-wise, ive been able to clean running issues up.

[babywag]

with a cheap usb setup and tunerpro on a laptop can datalog easily. burning a new chip(tuning) requires a chip burner.
can even buy bluetooth aldl and scan/datalog with an android phone these systems.

tons of info online about gm tbi conversions/tuning/etc.

the gm stuff has been around for decades and very well supported.

poor man's digital dash...(can datalog too)
Old phone + cheapy usb board + ALDLDroid

[Theodore]

Thanks, babywag. I appreciate it. Had never heard of any of that. Will take a look.

[Theodore]

Have been reading about ALDLdroid, TunerPro, etc, after looking at the ALDL port on the Wagoneer - there’s only 3 wires running to it (Ground, Diagnostic, & Check Engine Light)- Is it safe to assume that all It can do show codes via blinking the check engine light? Such that data logging, etc is not possible with this setup as it sits?




Found on obd-codes.com:

[babywag]

That's the later 8192 baud odbi plug diagram.

You should have the earlier 160 baud version.

All that is needed it 2 wires to datalog and a typical aftermarket gm tbi uses 3 wires.
A cheap usb->ttl converter board + usb cable or a more expensive aldl cable or bluetooth adapter is needed.

[Theodore]

Thanks for the advice. The 1320electronics Bluetooth ALDL setup is next on my list.

Also, a few days ago, I spoke with AFI & given the distributor I have is mechanical & not computer controlled, it was recommended that I reset initial timing to between 5&10 degrees advanced, and see how it works & go from there. I’ve not had a chance to get that done yet - have been tied up with the spring/shock/tire swap.

[Theodore]

Its been a while since last we talked about this. Since then, we've set initial timing, as well as, reading the Affordable Fuel Injection owners manual cover to cover, over & over, and as i've had time pulling data logs for analysis. Thanks for the recommendation re: the Bluetooth-enabled OBD1 scanner from 1320electronics.com. I've also picked up a timing light to set/check timing.

At this point, initial timing is set to 0 degrees (engine up to temp & set timing connector disconnected) which translates to 17 degrees timing advanced at idle. Am still seeing hesitation when we hit the throttle when cold. No hesitation issues when hot. Or, said differently, am seeing hesitation during Open Loop operation, and no issues once we get to Closed Loop. The interesting thing is: when the throttle is hit with the engine cold, the timing retards 10+ degrees or more for a split second. But, when hot: timing advances... Am thinking this is key to the issue, but the question is: why would timing retard when cold? What would cause this?

Am running AFI's TBI kit, where the ECM does not control spark; instead the Distributor has an ignition control module built into it.

Conditions when logs were pulled:
1) Date: 10/27 - outside temp was 68 degrees. Cold Start with a drive thru the neighborhood to town with 30mph speed limits. GW hesitates at every stop as we work our way to town.
2) Date: 11/09 - outside temp was 41 degrees: Cold Start had a rough idle for a few seconds, then once it settled out, we took the same route to town as log 1. Again, vehicle hesitates at every stop as we work our way to town. GW definitely ran worse at start time with the colder temp.
3) Date: 11/09 - freeway driving climbing a small mountain at speed. Can say, it's running the best it's ever run on the freeway. Can now climb a mountain at 70mph with throttle left vs. throttle floored and barely being able to maintain 55mph.

[Theodore]

Added the last data log in xlsx format. Thanks.

[KJ Ryu]

Our engines like a lot of advance on the timing. Mine is around 15deg, initial. Maybe try advancing it 3deg at a time and see how it drives. Or, get a cheap vacuum gauge and set timing so that the timing is just slightly shy of the spot where you get the most vacuum.

[KJ Ryu]

Our engines like a lot of advance on the timing. Mine is around 15deg, initial. Maybe try advancing it 3deg at a time and see how it drives. Or, get a cheap vacuum gauge and set timing so that the timing is just slightly shy of the spot where you get the most vacuum.

[babywag]

I am confused, if ecm isn't controlling timing why does it have (or need) a timing disconnect?
Timing should NOT be 0° initial if ecm is not controlling timing.
If engine hesitates when cold I would expect to see timing drop out? Since you state it is manually controlled & based on vacuum & mechanical.

I'll take a peek @ logs and see if anything jumps out.
But bump that initial timing up.

[Theodore]

I am confused, if ecm isn't controlling timing why does it have (or need) a timing disconnect?
Timing should NOT be 0° initial if ecm is not controlling timing.
If engine hesitates when cold I would expect to see timing drop out? Since you state it is manually controlled & based on vacuum & mechanical.

I'll take a peek @ logs and see if anything jumps out.
But bump that initial timing up.

Hey, Babywag - am confused, as well. The Frankenstein nature of the setup makes it hard to tell what i have - no shops want to touch it, so i'm on my own - hence, the crazy questions . Am going by what tech support at AFI told me - that ECM doesn't control spark. I asked about moving to a setup where ECM did control spark & it was recommended i not go there, given i had an existing/working system - which is debatable...

Poking around online, i found a post on gearhead-efi.com, you'd made asking about creating a fuel-only EFI setup, and was looking for a tach filter to finish it out http://www.gearhead-efi.com/Fuel-Inject ... or-1227747. Given my system dates to 2006, am wondering if it's not similar to what was being talked about there?

Also found an article that talks about fuel-only EFI - bullet #10, specifically talks about a hybrid distributor (original stalk mated to a GM cap, including an Electronic Spark Control, or Ignition Control Module). http://www.gearhead-efi.com/gm-ecm-pcm- ... rsion.html. Am thinking a fuel-only setup is what i have?

In the above gearhead-efi article, there's a mention of a 'tach filter' being required. I assume there's one somewhere, but so far i've not found it. Honestly, i don't know yet what i'm looking for.

[babywag]

Timing control isn't hard to add. Just some wiring and couple parts.
You need the hardware to read and burn a new chip though.
Or buy one...

Really need to reset initial timing though. If you're @ 0° that is a huge power killer.

[Theodore]

Our engines like a lot of advance on the timing. Mine is around 15deg, initial. Maybe try advancing it 3deg at a time and see how it drives. Or, get a cheap vacuum gauge and set timing so that the timing is just slightly shy of the spot where you get the most vacuum.

Am assuming that as part of this, similar to tuning w/a timing light, you'd still disconnect the 'set timing' wire, set initial timing & reconnect?

[Theodore]

Timing control isn't hard to add. Just some wiring and couple parts.
You need the hardware to read and burn a new chip though.
Or buy one...

Really need to reset initial timing though. If you're @ 0° that is a huge power killer.

Thanks for recommendation & patience with the questions - learning a lot in the process. ? - do you know, off-hand, what you have initial timing set to? So far, we've had initial set on the low end 0-5 & as far out as 17-18 initial, based on various recommendations - and, to date, the story reads like Goldilocks... sounds like we've just not hit 'just-right' yet.

Am looking into getting a vacuum gauge to hopefully zero-in on it to minimize the amount of tinkering required to get to 'just-right'.

[KJ Ryu]

Our engines like a lot of advance on the timing. Mine is around 15deg, initial. Maybe try advancing it 3deg at a time and see how it drives. Or, get a cheap vacuum gauge and set timing so that the timing is just slightly shy of the spot where you get the most vacuum.

Am assuming that as part of this, similar to tuning w/a timing light, you'd still disconnect the 'set timing' wire, set initial timing & reconnect?

I'm not familiar with your system so not sure what you mean by 'set timing' wire but, yes. Start at least 8deg advanced. Go up by 2 or 3 at a time til you hear pinging or feel power go back down, then back timing off a bit. Much faster if you have a vacuum gauge. Harbor Freight version works, even. Pretty much the same. Advance timing til it reads max vacuum, then back up a degree or two.

[KJ Ryu]

My carbed 360 is at 13ish and my EFI 401 is at 15deg initial, for reference; but both have been rebuilt and have no smog equipment.

[Theodore]

Thanks, KJ, Rju, ive just ordered a vacuum gauge from Amazon. Will be a few days before i can look at it. Gotta love tech; am on a plane, somewhere btw Boston & Atlanta... shopping for tools for the Jeep. Pretty cool.