BA 1.8 Astina hessitates only when hot??

bluetvrs1 · 30-11-2013, 08:43 PM

G'day fellow Mazda'ites,

My daughter has very tired 1997 auto 1.8 Astina with 180,000km on the clock with a strange problem that I was hoping someone could shed some light on. She doesn't have much money and taking it to a garage is the last option for her (1st option is dad of course

).

I've spent the day researching the internet for clues but nothing really matches the symptoms.

The car runs perfectly when cold but as soon as it's heated up the problem manifests itself. When accelerating from standstill the engine will baulk and almost stall unless you accelerate really gently. Once up to speed it runs fine.

I've checked for air leaks on the inlet side and checked the spark plugs..all good.
I changed the hose between the manifold and the air cleaner as that had a split...no difference.

When hot, I disconnected the oxygen (lamda) sensor....no difference.
When hot, I disconnected the engine temperature sensor...problem goes away (as far as I can tell by revving the engine in the garage)

Possible candidates as far as my limited knowledge allows would be: O2 sensor, TPS, airflow sensor (MAF), fuel filter?? I don't want to replace bits randomly as it will cost her but any suggestions as to likely candidates?

Many thanks in advance

project.r.racing · 01-12-2013, 10:03 AM

pretty common issue. starts to hesitate around 1500-3000 rpm, then come good after that right? using less than normal throttle prevents the issue from arissing right?

the spark plug leads will have a small hole in them in the solid section that goes down between the camshafts. when the engine heats up, the hole become large enough for spark to exit the lead going directly to the head, bypassing the plugs.

to test for this, once the engine it warm/hot. keep engine running and pull one lead out at a time. hold the solid section of the lead parrallel to the head about 5-10mm away. rotate on a few angles also.

if it comes out the bottom of the lead where it should, all good. if it comes out of anywhere else along the solid section, you have found your problem.

if it does end up being the leads, i have a new genuine set i've been trying to sell for a while. much cheaper than new cost.

bluetvrs1 · 02-12-2013, 09:49 PM

OK thanks for that projectR. I tried what you suggested but couldn't get a spark from the solid part of any lead. I might be interested in your leads anyway (can you send me a PM with price inc postage..I'm in NSW 2099) cheers.

It seems odd that it's only when hot which to me suggests a fueling problem. I took it out for a run tonight and as soon as it was warm it played up. I disconnected the temp sensor and it went back to driving normally again (as I guess it's not running so lean).

Since my first post I've replaced the fuel filter but that made no difference.
I've checked the diagnostic codes and they are clear. I know I'm checking them correctly as I get errors when I disconnect sensors.
I've measured the TPS and that gives a linear reading between 0.5v and 3.7v which I assume is within tolerance.

Tomorrow I'm going to clean the Mass Airflow Sensor (MAF) and see if that makes a difference.

rodhog · 03-12-2013, 12:48 AM

Well I'd agree on the leads but have you even just chucked a new set of plugs in.

project.r.racing · 03-12-2013, 07:15 AM

wow i would've bet money on it that the leads were the problem. i was that certain. maybe check then the whole lead, and the insulation around the dissy and cap for cracks.

NaughtyGT · 03-12-2013, 08:29 AM

Quote:

Originally Posted by bluetvrs1

G'day fellow Mazda'ites,.....My daughter has very tired 1997 auto 1.8 Astina with 180,000km on the clock .....

Tired @ 180k

Ok. You've replaced fuel filter & problem is still evident.

Try the following:

Spark Plugs (as Rod points out) Change them & see
AFM - either worn contact or fowled? Very gently clean with carb cleaner
Vacuum leak - difficult to find leak. Google procedure is the quickest way

Old Grey · 03-12-2013, 05:05 PM

O2 sensor can be cleaned by heating the tip on a burner until red.

bluetvrs1 · 03-12-2013, 08:26 PM

Problem solved

I did three things today.

I took off the dizzy cap and all four contacts looks pitted and worn. Cleaned these up with emery cloth (over a flat blade). This seemed to improve the hot running but the problem was def still there.

I then changed the HT leads (sorry project.R I didn't read your PM until I got home and I'd already been to the motor factors by then). This didn't make any improvement to the hot running at all.

I then installed a new set of plugs and the hot running issue went away.The old plug contacts looked ok but the ceramic insulator had brown 'burn' marks (on the ceramic) where the ceramic meets the metal case. Putting the plug back into a lead I could see the burn marks stopped exactly where the end of the HT lead is so I assume the metal case was arc'ing the 1cm distance to the HT lead end. All four plugs were in this condition. I wish I could upload a photo to be more clear...

In conclusion I think it was a problem with the HT lead insulation and this has affected the spark plugs. At the weekend I might try putting the old leads back on with the new plugs....for my own curiosity. There is probably still a residual issue with the dizzy cap but I'll see how it runs for a while before spending anymore money on it.

Many, many thanks to all contributors who helped on this one....I thought it was a fuel issue but you were right in predicting the ignition.

30-11-2013, 08:43 PM	#1
bluetvrs1 Junior Member Join Date: May 2010 Location: sydney Car: Jeep, Kawasaki Posts: 11	BA 1.8 Astina hessitates only when hot?? G'day fellow Mazda'ites, My daughter has very tired 1997 auto 1.8 Astina with 180,000km on the clock with a strange problem that I was hoping someone could shed some light on. She doesn't have much money and taking it to a garage is the last option for her (1st option is dad of course ). I've spent the day researching the internet for clues but nothing really matches the symptoms. The car runs perfectly when cold but as soon as it's heated up the problem manifests itself. When accelerating from standstill the engine will baulk and almost stall unless you accelerate really gently. Once up to speed it runs fine. I've checked for air leaks on the inlet side and checked the spark plugs..all good. I changed the hose between the manifold and the air cleaner as that had a split...no difference. When hot, I disconnected the oxygen (lamda) sensor....no difference. When hot, I disconnected the engine temperature sensor...problem goes away (as far as I can tell by revving the engine in the garage) Possible candidates as far as my limited knowledge allows would be: O2 sensor, TPS, airflow sensor (MAF), fuel filter?? I don't want to replace bits randomly as it will cost her but any suggestions as to likely candidates? Many thanks in advance

01-12-2013, 10:03 AM	#2
project.r.racing Senior Member Join Date: Sep 2004 Location: n/a Car: n/a Posts: 10,929	pretty common issue. starts to hesitate around 1500-3000 rpm, then come good after that right? using less than normal throttle prevents the issue from arissing right? the spark plug leads will have a small hole in them in the solid section that goes down between the camshafts. when the engine heats up, the hole become large enough for spark to exit the lead going directly to the head, bypassing the plugs. to test for this, once the engine it warm/hot. keep engine running and pull one lead out at a time. hold the solid section of the lead parrallel to the head about 5-10mm away. rotate on a few angles also. if it comes out the bottom of the lead where it should, all good. if it comes out of anywhere else along the solid section, you have found your problem. if it does end up being the leads, i have a new genuine set i've been trying to sell for a while. much cheaper than new cost.

02-12-2013, 09:49 PM	#3
bluetvrs1 Junior Member Join Date: May 2010 Location: sydney Car: Jeep, Kawasaki Posts: 11	OK thanks for that projectR. I tried what you suggested but couldn't get a spark from the solid part of any lead. I might be interested in your leads anyway (can you send me a PM with price inc postage..I'm in NSW 2099) cheers. It seems odd that it's only when hot which to me suggests a fueling problem. I took it out for a run tonight and as soon as it was warm it played up. I disconnected the temp sensor and it went back to driving normally again (as I guess it's not running so lean). Since my first post I've replaced the fuel filter but that made no difference. I've checked the diagnostic codes and they are clear. I know I'm checking them correctly as I get errors when I disconnect sensors. I've measured the TPS and that gives a linear reading between 0.5v and 3.7v which I assume is within tolerance. Tomorrow I'm going to clean the Mass Airflow Sensor (MAF) and see if that makes a difference.

03-12-2013, 12:48 AM	#4
rodhog Senior Member Join Date: May 2005 Location: Sydney Lakemba Car: mx-6 626 Gs300 Maz2 was 95 KF BA-HT Posts: 2,024 View Photos By: rodhog	Well I'd agree on the leads but have you even just chucked a new set of plugs in.

03-12-2013, 07:15 AM	#5
project.r.racing Senior Member Join Date: Sep 2004 Location: n/a Car: n/a Posts: 10,929	wow i would've bet money on it that the leads were the problem. i was that certain. maybe check then the whole lead, and the insulation around the dissy and cap for cracks.

03-12-2013, 05:05 PM	#7
Old Grey Junior Member Join Date: Apr 2009 Location: Sydney Car: Astina BG 1991 - Rx7 S4 Posts: 105	O2 sensor can be cleaned by heating the tip on a burner until red.

03-12-2013, 08:26 PM	#8
bluetvrs1 Junior Member Join Date: May 2010 Location: sydney Car: Jeep, Kawasaki Posts: 11	Problem solved I did three things today. I took off the dizzy cap and all four contacts looks pitted and worn. Cleaned these up with emery cloth (over a flat blade). This seemed to improve the hot running but the problem was def still there. I then changed the HT leads (sorry project.R I didn't read your PM until I got home and I'd already been to the motor factors by then). This didn't make any improvement to the hot running at all. I then installed a new set of plugs and the hot running issue went away.The old plug contacts looked ok but the ceramic insulator had brown 'burn' marks (on the ceramic) where the ceramic meets the metal case. Putting the plug back into a lead I could see the burn marks stopped exactly where the end of the HT lead is so I assume the metal case was arc'ing the 1cm distance to the HT lead end. All four plugs were in this condition. I wish I could upload a photo to be more clear... In conclusion I think it was a problem with the HT lead insulation and this has affected the spark plugs. At the weekend I might try putting the old leads back on with the new plugs....for my own curiosity. There is probably still a residual issue with the dizzy cap but I'll see how it runs for a while before spending anymore money on it. Many, many thanks to all contributors who helped on this one....I thought it was a fuel issue but you were right in predicting the ignition.