KN Laser bad hesitation when warmed up - Please help!

[smithy8187]

Hey all,

Hope I'm in the right section of forum. I have a KN Laser 1.8l automatic, which is same as the Protege AFAIK. I have an issue with my Laser that is literally driving me insane..

When I first drive the car when cold it runs like a dream, but when the temp gets to normal operating temp, that's when it starts to hesitate and sound like it's running on 3 cylinders.

It will do this when there is very little inlet manifold pressure it seems, ie when cruising at say 70 and I just lightly put my foot on the accelerator it will jerk and cough, OR if I am at a roundabout standing still and I stomp on the throttle, it will go bababababa and then clear itself out and drive normal.

So far I have changed the following:
Plugs
Leads
Coil packs (2 of)
MAF sensor
Bosch fuel pump
Fuel filter
Throttle body to air intake pipe a couple of years ago

I have checked over all vacuum lines, brake booster lines, throttle body piping. I have checked under the car, I have checked for air leaks with a funnel/pipe. There is a very slight hiss from around the throttle body area but I can't pin point it with the funnel/pipe, it might even be a normal noise? Possible intake manifold gasket?

The funny thing is, is if I remove the temp sensor plug, it runs perfect even when warm, with no hesitation whatsoever. So hopefully this bit of info can help in fixing the issue?

I am almost at the point of giving up. It's disappointing throwing parts at it just to have it run like crap again. It actually ran worse with the new MAF sensor. But I don't want to keep buying the same new parts in chance that I got a dud.

I thought of injectors but why would it run beautiful with temp sensor unplugged?

Has anyone got any ideas? Please help as this is killing me

Thanks

Edit: The idle is fine too, it's only when I accelerate.

 

[smithy8187]

Come on folks! Over 200 views and no replies, surely someone must have an idea? Let's hear it

 

[smithy8187]

Nearly 400 views now! Lets see if we can break the record of most views with 0 replies.

 

[smithy8187]

Captain's log, stardate 13062024. I'm thinking it may be vacuum related because when I changed the MAF sensor it seemed to run worse, even when putting the old one back in. I just rechecked all the lines but alas couldn't find anything, but it could be the one going from the brake booster to manifold as it's got another rubber pipe over the top of it. Maybe it's cracked underneath? If that doesn't work I will take it to a mechanic and get them to do a diagnostic. It's definitely running worse now, it won't even hold idle when still. Least it will be easy to diagnose. Will report back.

 

[smithy8187]

Captain's log, stardate 17062024. I changed the spark plugs again since it was longer than I thought when I last changed them, and not to my surprise it still ran like a dog. I disconnected the battery so in the morning I'll connect it again. I think I've tried disconnecting battery in the past and letting it sit and it helped a bit resetting the computer. I do now have her booked into a decent mechanic next week so hopefully they will find something. My money is on a vacuum leak. Plugs are changed so thats one thing they don't need to check. It's fun pulling up to traffic lights with my foot on the accelerator to stop it stalling. Over and out.

 

[Mazdiod2]

I knew someone with an early 90's that had a crack in the plastic accordian air intake connector that would stall when the motor shifted slightly and the crack would open.

 

[pcb]

The funny thing is, is if I remove the temp sensor plug, it runs perfect even when warm, with no hesitation whatsoever. So hopefully this bit of info can help in fixing the issue?

I remember someone that was having a similar issue.
It turned out that the temperature sensor was covered in crap so the sensor wasn't getting a proper reading.

He removed his sensor, cleaned the corrosion off with a wire brush and that fixed the problem.
(You'd maybe just want to replace it.)

 

[smithy8187]

I knew someone with an early 90's that had a crack in the plastic accordian air intake connector that would stall when the motor shifted slightly and the crack would open.

I actually changed that big intake pipe a few years ago. I did take it off when I checked my vacuum lines and checked it for any cracks but it was fine.

I remember someone that was having a similar issue.
It turned out that the temperature sensor was covered in crap so the sensor wasn't getting a proper reading.

He removed his sensor, cleaned the corrosion off with a wire brush and that fixed the problem.
(You'd maybe just want to replace it.)

That's interesting. I might need to try that. The last couple of days it's been idling really low (enough to stall in drive) when I start it on a cold morning - BUT the babababababa running on 1 cylinder thing only happens when engine is warm.

Disconnecting the battery overnight did nothing but wasn't getting my hopes up with that. It goes in on Monday so 'hopefully' they find something.

 

[pcb]

Keep in mind that the ECU needs to relearn how to idle the car after the battery is disconnected.

Rough Idle, Loss of Power and No CEL (2003 Protege5) - Solved!

Hello I've used this website multiple times when troubleshooting my P5. For information on the car it's a 2003 MP5 130000 miles, automatic transmission. I've replaced the spark plugs, ignition coil packs, spark plug wires, fuel injectors all around 128000 miles when I had issues with misfires...

mazdas247.com

 

[smithy8187]

Keep in mind that the ECU needs to relearn how to idle the car after the battery is disconnected.

Rough Idle, Loss of Power and No CEL (2003 Protege5) - Solved!

Hello I've used this website multiple times when troubleshooting my P5. For information on the car it's a 2003 MP5 130000 miles, automatic transmission. I've replaced the spark plugs, ignition coil packs, spark plug wires, fuel injectors all around 128000 miles when I had issues with misfires...

mazdas247.com

Thanks for linking that thread. So other contenders could also be IAC valve or 02 sensor? I haven't quite done 100 miles for the computer to learn to idle, but the hesitation is the main worry.

When I am at traffic lights with my foot on the brake and accelerator to bring the idle around 1000rpm, I can hear it missing every second or so like it has a lumpy cam.

 

[smithy8187]

Captain's log, stardate 24062024. Was booked in to mechanic today. They didn't have the right diagnostic to fit the plug so they couldn't check any faults. They noted the fuel gauge went to zero when testing so possible fuel pump wiring problem.. but I changed the fuel pump a few weeks ago and plugged it all in properly. It didn't run better or worse after I changed them. They also cleaned idle air control valve and pipes with no improvement. They recommended an auto elec for the proper plug, but when I rang they don't do engine diagnostics anymore. Will hunt for more tomorrow and try to get it booked in. Pain in the ass. Hopefully the car survives driving on 1 cylinder till it gets checked again.

 

[smithy8187]

So after more digging, you can use an LED and a jumper wire in the diagnostic plug. The flashes that it spat out was, first batch: 11, 15, 10, 14. Second batch: 11, 15, 12, 13. According to Mr chatGPT, it's problems with the crank position sensor, wiring issues or electrical connections, and ECU memory issues. Going to chuck in a new crank position sensor, check wiring/connections etc and go from there..

 

[smithy8187]

Captain's log, stardate 25062024. Ok so I disconnected battery, replaced CAS, and there was an earth going from engine mount to body that was very loose so I tightened it. To my surprise, the running on 1 cylinder when taking off has completely gone which is bloody brilliant. But it's still idling low and sometimes stalling when coming to a stop. The LED blinks now read 11, 15, 12, 13, so there is still problem with ECU/wiring to it. Will keep fighting.

 

[smithy8187]

Alrighty, slowly getting there I think. Car went to another mechanic and did a smoke test on the inlet manifold. Smoke was coming out of the throttle body butterfly shaft...where it comes through the side of throttle body, but he didn't know if it was normal or not, and also didn't think it was the main problem.

He cleaned out the IAC again because he showed photos of it pretty dirty, even though the last mechanic said they cleaned it. Also put a new gasket on the TB. There was also an exhaust manifold leak which he fixed. Compression was fine which was good to know.

But...when he pulled the spark plugs, cylinder 1 and 2 plugs were black and fouled. The plugs I put in a couple weeks ago. He reckons it might be dirty or bad injectors and to run decent injector cleaner in the fuel at 1/4 tank, if that doesn't work then take them out and get them tested by a shop.

I looked at the injectors when I worked on the car a few weeks ago and saw that 1 and 2 injector were a different color to 3 and 4 injector but didn't think anything of it.. Car is nearly at quarter tank so will run the stuff and see how I go.

After all that work it runs a little bit better. It doesn't stall any more but still a bit low idle and laggy to take off.

 

[smithy8187]

This will be my last log. Hopefully any future travelers from Google might stumble upon this and it might help them.

I put the fuel injector cleaner in and it seemed to help more with the idle but it was still not 100%. For sh1ts and giggles I put my old MAF sensor back on and the lagging problem seemed to disappear (after I put the new MAF on I had problems really low idle and not running right). It has very very slight miss so I might still pull the injectors and get them tested. The lagging has fully gone away and takes off like its old zippy self again. Have disconnected the battery again and will see what codes it shows.

Thanks @Mazdiod2 and @pcb for your help.

 

[pcb]

I used Seafoam to flush my engine when I bought my car, then used half a can in with the new oil at every 5,000 km oil change.

I also put some up the brake booster vacuum line, and then a shot or two in with the gas at every fill up.

My car always ran smoothly and my engine didn't burn a drop of oil.

I had a smog test about 10 years ago where they sniffed the tailpipe, (before they started plugging into the OBDII port) and the guy came out of the shop with a big smile on his face.

He said sorry, I had to do the test twice. I thought my machine was broken, I couldn't get a reading.

He said my car pollutes less than when the car was new.

 

[smithy8187]

I used Seafoam to flush my engine when I bought my car, then used half a can in with the new oil at every 5,000 km oil change.

I also put some up the brake booster vacuum line, and then a shot or two in with the gas at every fill up.

My car always ran smoothly and my engine didn't burn a drop of oil.

I had a smog test about 10 years ago where they sniffed the tailpipe, (before they started plugging into the OBDII port) and the guy came out of the shop with a big smile on his face.

He said sorry, I had to do the test twice. I thought my machine was broken, I couldn't get a reading.

He said my car pollutes less than when the car was new.

Hah gees. Funny I was thinking of using Seafoam on my other older car. Some people really swear by it.

 

[pcb]

If you want to prevent this from happening to your pistons then I think you should try and keep it clean.

There's not too much you can do once the oil drain holes are plugged, then the oil rings seize up and your engine starts burning oil like a MoFo.

Smoke on cold start

Bumping the thread back, with some good/bad news... Well, the good news is: I found the problem of cold start smoke. Bad news: Well, it's the rings... Worse news: The rings are fine, not worn out, not scored, not broken...So, what is it then? Ok, here's the details: Mazda's pistons are...

mazdas247.com

 

[pcb]

He reckons it might be dirty or bad injectors and to run decent injector cleaner in the fuel at 1/4 tank,

That's what I did with the Seafoam when I first got my car.
I think I used ½ a bottle in the gas tank and ½ a bottle up the brake booster vacuum line.
Then a shot in the gas at every fill up ever since.
Cheap and easy to do.

I put the fuel injector cleaner in and it seemed to help more with the idle but it was still not 100%.

I had a 1982 Mazda GLC that started running like crap so I took it to Mazda and they suggested a carburetor rebuild costing over $400.

I told the mechanic at work about it and said to try a bottle of fuel injecor cleaner.
A $2 bottle of fuel injector cleaner fixed my car.

I use the Seafoam to keep everything clean. It cleans the injectors and keeps the combustion chambers clean, and it cleans the rest of the engine so it doesn't start burning oil.
That helps keep the IAC and especially the EGR valve from gumming up from oil in the exhaust.

Oil in the exhaust can burn out pre-cats and foul O2 sensors too.



One thing that I heard that can go wrong with Seafoam is that if you have a Really dirty engine or fuel system, the Seafoam can dissolve and dislodge a Huge blood clot and your car will suffer a heart attack or stroke.

A neighbor told me that his really old car started burning oil after using Seafoam.
It turned out that the gunk built up on the valves seals was what was sealing them, and they leaked after washing away the goo.