1FZ dies right after startup when cold. Works fine when warmer. (1 Viewer)

[TurboDennis]

Replaced a blown 1FZ (cracked head) on a 1997 truck with a used 1FZ.

The truck ran perfect until the head cracked. The replacement 1FZ was pulled from a running truck, which i tested personally before pulling. ~175psi compression (+/- 3psi) in all 6 cylinders.

After the "new" engine was installed, it has the following issue:

Starts easy, but stalls within 1 second. On second attempt its HARD to start, takes a good 4-7 seconds of cranking. Once it starts, it either struggles to run (running very rough at ~300-400 rpm) and stalls again, or struggles for 10 seconds or so and eventually idles up and runs fine after that.
Once the engine runs for about a minute or so, it runs beautifully and restarts easy (if asked to), until it cools down completely. After it does, the exact same thing repeats.


Any ideas?

 

[Kamran Khan]

Try cleaning egr valve and check if vacuum switch valve is functioning properly. Also when your car warms up unplug MAF sensor, after unplugging MAF if your car dies that would mean MAF is functioning properly, if it is still runing replace MAF.

 

[TurboDennis]

Thanks for the suggestions. I'll try swapping the VSV and EGR from the original blown engine to see if it helps.
I did not change the MAF when i swapped the engine, so i'm pretty sure that MAF isnt the problem.

 

[jonheld]

Try cleaning egr valve and check if vacuum switch valve is functioning properly. Also when your car warms up unplug MAF sensor, after unplugging MAF if your car dies that would mean MAF is functioning properly, if it is still runing replace MAF.

This statement makes no sense.
If the MAF is good, unplugging it should cause the fuel pump to shut down. However if the truck continues to run without the MAF, then how could the MAF be the issue? You just removed it from the system.

 

[Jgrauman]

Agree with maf issue.

 

[bajaphile]

I take it no codes.
I'd probably start checking all the grounds. All your electrical connections are nice and snug and clean? Check ignition system connections.

Double check you didn't forget to connect a vacuum hose or ensure your vacuum hoses are connected properly.

 

[ajax1]

Hard start on cold can be your injectors make sure you didn’t cut oring they should move freely with a little resistance, or your losing fuel pressure somewhere

 

[Tools R Us]

CEL on, if so what code(s)?

 

[TurboDennis]

Thanks to everyone who replied. I didnt have time to mess with the truck until today. I spent a lot of time on it today and checked a variety of things, without finding the cause of the problem.
Things i did:

-Checked all vacuum lines and ground wires. All good.
-Removed, cleaned, tested the EGR valve. Works as it should. I also tried blocking off the port on the intake manifold where the EGR valve connects, along with all vacuum lines, essentially disabling the EGR system entirely. Didnt solve the issue. So i know that the issue is not related to EGR valve, EGR modulator or EGR VSV
- Replaced ISC valve with a known working one.
- Replaced and adjusted TPS with a known working one.
- Repalced FPR with a known working one.
- Tried applying and cutting off vacuum manually to FPR to eliminate the possibility of a bad FPR VSV.

None of these things helped with the problem described in OP.

I also know for a fact that MAF sensor, ECU, WIRING harness are not at fault, because i didnt replace them along with the "new" engine and they worked fine before.

As for CEL, im pretty sure that my OBD2 scanner crapped out. It doesnt want to connect to ECU on this particular truck (works fine on other cars). So i cant pull the codes until i get a new code reader. The CEL is on, but it was on forever due to EVAP issues long before i put this new engine in.

One thing i noticed is that when the truck is started (on second attempt) and idling very rough (on the verge of stalling), even touching the throttle lightly will instantly kill it. Once it warms up a bit and the issue goes away completely and it seems to run normally.

 

[Jgrauman]

Thanks to everyone who replied. I didnt have time to mess with the truck until today. I spent a lot of time on it today and checked a variety of things, without finding the cause of the problem.
Things i did:

-Checked all vacuum lines and ground wires. All good.
-Removed, cleaned, tested the EGR valve. Works as it should. I also tried blocking off the port on the intake manifold where the EGR valve connects, along with all vacuum lines, essentially disabling the EGR system entirely. Didnt solve the issue. So i know that the issue is not related to EGR valve, EGR modulator or EGR VSV
- Replaced ISC valve with a known working one.
- Replaced and adjusted TPS with a known working one.
- Repalced FPR with a known working one.
- Tried applying and cutting off vacuum manually to FPR to eliminate the possibility of a bad FPR VSV.

None of these things helped with the problem described in OP.

I also know for a fact that MAF sensor, ECU, WIRING harness are not at fault, because i didnt replace them along with the "new" engine and they worked fine before.

As for CEL, im pretty sure that my OBD2 scanner crapped out. It doesnt want to connect to ECU on this particular truck (works fine on other cars). So i cant pull the codes until i get a new code reader. The CEL is on, but it was on forever due to EVAP issues long before i put this new engine in.

One thing i noticed is that when the truck is started (on second attempt) and idling very rough (on the verge of stalling), even touching the throttle lightly will instantly kill it. Once it warms up a bit and the issue goes away completely and it seems to run normally.

I would clear the codes if there were pre existing ones first to make sure you chase the right problem. Weird your reader works on others but not this one, may have an ecu issue after all. But clear the codes, let it run and see if another code pops, the get a good reader and see what's up. Also, really seems like an airflow issue, may try another maf if you have a spare

 

[MoJ]

[QUOTE="zzdenis, post: 11709862, member: 124410]

As for CEL, im pretty sure that my OBD2 scanner crapped out. It doesnt want to connect to ECU on this particular truck (works fine on other cars). [/QUOTE]

If the scanner connects on other cars but not the 80 it’s not an issue with the scanner.

 

[TurboDennis]

If the scanner connects on other cars but not the 80 it’s not an issue with the scanner.

Scanner does not connect to 80's. I have another 80 and it wont connect to it either. It connects to all other brands/models that i've tried. I think its a problem with the specific OBD2 protocol that 80's use. Either way, i have a new scanner on the way.

 

[danthman114]

kinda sounds like a fuel problem. clogged injectors maybe?

 

[TurboDennis]

I thought about it being an issue with injectors, but why would it go away completely after it warms up a little?

 

[Kamran Khan]

My next guess is Idle Air control Valve, it's very easy to uninstall. Maybe clean that or swap it with your old engine.

 

[Kamran Khan]

Spray lots of carburetor cleaner into you car's idle air control valve but I suggest disassemble IACV first and then clean it. Also make sure throttle body gasket is not leaking. Clean throttle body as also.

 

[bigredmachine]

will it start and run if you hold the throttle open, if so its probably the iac that's starting to go bad

 

[Seth_O]

I had a similar issue after replacing a HG on my '80. Started fines but sluggish at slow speeds and rough running until it warmed up.

Ended up needing to tighten the TB further. Check for gaps in metal-to-metal connections. I hooked a shop vac (in blow mode) up to my intake to hunt for vacuum leaks.

Dont assume that because something was functioning before the work it still is. A head replace causes you to get into a LOT of components.

 

[TurboDennis]

My next guess is Idle Air control Valve, it's very easy to uninstall. Maybe clean that or swap it with your old engine.

will it start and run if you hold the throttle open, if so its probably the iac that's starting to go bad

IACV valve was replaced with a known working one, as i said in post #9. (I referred to it as ISC valve (Idle Speed Control))

I had a similar issue after replacing a HG on my '80. Started fines but sluggish at slow speeds and rough running until it warmed up.

Ended up needing to tighten the TB further. Check for gaps in metal-to-metal connections. I hooked a shop vac (in blow mode) up to my intake to hunt for vacuum leaks.

Dont assume that because something was functioning before the work it still is. A head replace causes you to get into a LOT of components.

I will try to look for leaks using the shop vac (or compressed air) method. Im running out of ideas, so it's worth a try.
BTW, head or intake manifold has not been removed on this engine.





I did get a new code reader and was able to pull codes from it:
P0115 (Coolant temp sensor malfunction) - Not sure why, as the temp gauge seems to work fine
P0120 (TPS circuit malfunction) - Again, strange as i replaced and tested/adjusted TPS
P0135 (O2 sensor) had the issue before the swap, didnt cause any noticeable issues
P0141 (02 sensor)
P0135P (02 sensor)
P0141P (02 sensor) Not sure what the "P" at the end of the code means.

 

[TurboDennis]

Update. Checked for vacuum leaks by pressurizing the intake and then again using propane and none were found.

Replaced distributor cap, rotor, wires and spark plugs with known good ones. Nothing changed.

I officially ran out of ideas.

One weird thing that i noticed is that there is absolutely no change in engine speed/sound when oil cap is removed with the engine running, and no vacuum is felt. Other 80's that i had would either struggle or die with the oil cap removed.